Spectrum and energy levels of four-times ionized zirconium (Zr v)

the ng G (n = 6-9) series to determine the first ionization limitof this ion. The best fit for the ns 3S, series gives 151862.5cm- 1 . A fit to the four ng levels gives 151 862.9 cm-l. In-clusion of the 5g level into the fit also gives 151862.9 cm -1We therefore give the value for the ionization energy of singlyionized aluminum as 151862.7(4) cm- 1 or 18.82873(5) eV.

'F. Paschen, "Die Funkenspektren des Aluminiums. Teil II," Ann.Phys. (Leipz.) 71, 537-561 (1923).

2R. A. Sawyer and F. Paschen, "Das erste Funkenspektrum des Alu-miniums A II," Ann. Phys. (Leipz.) 84, 1-19 (1927).

3F. Paschen and R. Ritschl, "Infrarote Gitterspektren und Spek-tralgesetze (AlII, AlI, HeI und II, Znii, Zni) " Ann. Phys. (Leipz.)18, 867-892 (1933).

4A. G. Shenstone and H. N. Russell, "Perturbed series in line spectra,"Phys. Rev. 39, 415-434 (1932).

5 J. H. Van Vleck and N. G. Whitelaw, "The Quantum Defect ofNonpenetrating Orbits, with Special Application to Al II," Phys.Rev. 44,551-569 (1933).

6C. E. Moore, Atomic Energy Levels, Nat. Stand. Ref. Data Ser., Natl.Bur. Stand. (U.S.), 35, Vol. I, 126-128 (1971).

7V. Kaufman and B. Edl6n, "Reference wavelengths from atomicspectra in the range 15 to 25000 A," J. Phys. Chem. Ref. Data 3,825-895 (1974).

8J. Junkes, E. W. Salpeter, and G. Milazzo, "Atomic Spectra in theVacuum Ultraviolet, Part one," Specola Vaticana (1965).

9A. W. Weiss, "Theoretical Multiplet Strengths for MgI, AlII, andSi III," J. Chem. Phys. 47, 3573-3578 (1967).

'0 R. N. Zare, "Correlation Effects in Complex Spectra. II. Transi-tion Probabilities for the Magnesium Isoelectronic Sequence," J.Chem. Phys. 47,3561-3572 (1967).

"A. W. Weiss, "Calculations of the 2sns 'S and 2p3p 3"1P of BeI,"Phys. Rev. A 6, 1261-1266 (1972).

"K. T. Lu, "Quantum-defect analysis of the effects of np2 terms onthe singlet terms of alkaline earths and of their isoelectronic se-quences," J. Opt. Soc. Am. 64, 706-711 (1974).

3A. W. Weiss, "Series perturbations in atomic spectra: Superposi-tion-of-configurations calculation on Al I and Al II," Phys. Rev. A9, 1524-1536 (1974).

14F. Paschen, "Erweiterung der Spektren Al II, Mg I, BeI und Al I,"Ann. Phys. (Leipz.) 12, 509-527 (1932).

5M. Heyden and R. Ritschl, "Uber das Kernmoment des Alumini-ums," Z. Phys. 108, 739-747 (1938).

16S. Suwa, "Anomalous Hyperfine Structure in the Spectrum of Al II,"J. Phys. Soc. Jpn. 6, 231-238 (1951).

Spectrum and energy levels of four-times ionized zirconium(Zr v)

Joseph Reader and Nicolo AcquistaNational Bureau of Standards, Washington, D.C. 20234

(Received 29 September 1978)

The spectrum of zirconium was observed in the region from 200 to 2670 A with a sliding-sparkdischarge on the 10.7-mi normal- and grazing-incidence spectrographs at NBS. About 580 lines wereassigned to Zr v. From these observations the energy level system of Zr v (Kr I isoelectronic sequence,ground state 4s 24p

6 'S 0) has been extended to the complete 4s 2 4p 5 5 s, 6 s, 7s, 5p, 4d, 5d, 4f, 5g,and 4 s 4p 6 4d configurations and the nearly complete 4s 24p

5 6d and 6 g configurations. About 330lines have been classified. All observed configurations have been theoretically interpreted. The en-ergy parameters determined by least-squares fits to the observed levels are compared with Hartree-Fock calculations. The ionization energy derived from the 4p 5 n g, n = 5,6 levels is 648 050 - 60cm-' (80.349 - 0.007 eV).

The spectrum of the krypton-like ion Zr v was first inves-tigated by Chaghtai,l who identified several resonance linesof the type 4p 6 -4p 5 nl in the 200-400 A region. In 1972,Reader, Epstein, and Ekberg2 revised and extended this sys-tem of resonance lines. This established the J = 1 levels fora number of excited configurations.

In the present work we observed transitions between theexcited configurations of Zr v and determined the completelevel structures of the principal excited configurations. Theresults confirm the identifications of Ref. 2 and provide adetailed understanding of the interaction between the 4p54dand 5s configurations.

EXPERIMENT

The spectra were excited in a low-voltage sliding spark,operated as described in Ref. 2. The electrodes consisted ofmetallic zirconium rods. The spacer was made of quartz. At

239 J. Opt. Soc. Am., Vol. 69, No. 2, February 1979

a peak current of 500 A the fifth spectrum was greatly en-hanced relative to spectra of other stages of ionization.

In the region from 500 to 2670 A the spectra were recordedon our 10.7-m normal-incidence spectrograph. The gratinghad 1200 lines/mm, providing a plate factor in the first orderof 0.78 A/mm. Below 500 A the spectra were recorded on our10.7-m grazing-incidence spectrograph. The angle of inci-dence was 800. The grating had 1200 lines/mm, providing aplate factor in the first order of 0.25 A/mm at 350 A.

Wavelength calibration in the region from 600 to 2670 A wasobtained from spectra of CUI13 excited in a hollow-cathodedischarge. Below 600A wavelength calibration consisted ofspectra of YIII-VI excited in a sliding spark. (The spectrumof yttrium from a sliding spark is currently being developedas a source of reference wavelengths in our laboratory. 4

Values accurate to a few thousandths of an A have been givenfor Y III,5 Y IV,2 Y V,6 and Y VI,7 but most of the wavelengthsare as yet unpublished.) To correct for shifts between ref-

239

TABLE!. Observed spectral lines of Zrv. All wavelengths are in vacuum. Except for the 4p0 , 4s4pG4d, and 4s4p5 5p configurations, the levels given

for the line classifications are all based on the 4p5 2p core. The 4p6 , 4p5 4d, 4s4p6 4d, and 4s4p 6 5p configurations are designated in LS coupling, all

others in J11. Symbols: p. perturbed by close line; u, unresolved from close line.

Wave WaveWavelength Inten- number Wavelength Inten- number

(A) sity (cm-') Classification (A) sity (cm-') Classification

165.257168.943170.392171.403174.286175.016176.043180.988183.042186.146188.027189.248204.798209.872211.339216.307220.310280.779284.333292.187294.570294.938295.159297.480297.779298.190298.316298.427298.533298.813298.946298.979299.399299.663299.890300.391300.673300.748301.587301.634301.958302.150302.505303.380303.752303.831304.008304.076304.142304.380304.414304.527305.236305.425305.459306.698306.904

307.236307.753308.321

11213227

20305025p80

100100125304020p

30030407060p30p705070807 0 p303030305060p30p40p2 0p50p80p205020p2030p

5006080p302080p

30030703060p3060p50p

605118591916586882583420573770571377568042552522546323537 213531839528406488286476480473173462306453906356 152351700342246339478339054338800336158335797335357335215335090334971334658334509334472334002333708333456332 884.5332587.5332504.5331579.7331527.5331 171.8330961.0330572.8329619.9329215.5329 130.1328938.7328864.6328794.2328536.6328499.7328377.8327 615.4327 412.8327 676.1326028.5325834.4325482.8524 936.2324337.1

4p 6 'So- lOs 3/2[3/2]j4p 6 1So-9s 3/2[3/214p 6 'So-8s 1/2[1/2];4p 6 'So-7d 1/2[3/2];4p 6 ISo-4s4p 6 5p 'P;4 p 6 'So- 8s 3/2[3/2];4p6 'So-7d 3/2[3/2];4p 61So-7s 1/2[1/2];4p 6 'So-6d 1/2[3/2];4 p 6 ISo- 7s 3/2[3/2];4p6 'So-6d 3/2[3/2];4p 6 ISo-6d 3/2[1/2];4p 6ISo-6s 1/2[1/2];4p 6 'So-5d 1/2[3/2]f4p6 SO - 6s 3/2[3/2];4 p 6 1So-5d 3/2[3/2];4 p 6 1So-5d 3/2[1/2];

4p 61So-5s 1/2[1/21;

4p 6 1So-4d P'I

4p 6ISo-5s 3/2[3/2];

308.489308.621308.857309.421309.728310.326310.508310.928311.252312.100313.050313.954314.488314.628315.308315.440317.280317.298319.842321.845322.954322.999324.785325.030325.213325.410326.087327.536329.271329.752330.217330.528330.851331.789332.316333.007333.232333.945334.863335.233337.670337.932341.002346.419356.429356.528362.226368.184368.441372.724373.218376.582377.293378.680378.935383.917386.214386.866388.330389.971


go60203015p3010906020308090507020p40406010103070p705030p8030p30p202030601030p306060p3

1040203020402030

400p30plop201010lop304030158020

324161.1324021.9323744.8323 184.7322863.7322 242.0322053.3321618.3321283.4320409.7319437.3318518.3317 976.7317835.7317 149.9317017.5315179.0315 161.1312654.4310708.7309670.4309 598.9307 896.4307663.9307 490.7307304.8306 666.3305 309.7303701.3303 258.6302 831.2302546.3302256.6301396.5300918.1300 294.1300091.0299450.2298 629.4298299.5296147.2295917.6293253.5288668.2280 560.7280483.0276070.4271603.3271413.9268295.0267939.6265 546.4265046.6264075.2263897.4260473.0258924.0258487.7257 512.9256429.3

4p6 1So-4d 3D;

Joseph Reader and Nicolo Acquista 240

TABLE I. (Continued)


(A) sity (cm-1) Classification (A) sity (cm-') Classification

390.740391.804392.248392.926394.546397.024399.107410.425410.572411.291429.983442.963453.610456.425458.698460.549461.009462.852468.577469.917470.078470.558477.364482.745483.060483.231483.902485.632486.454488.571488.929490.694491.628491.804491.993492.331494.077494.629496.338498.046499.471499.535502.361508.727509.218509.896513.027513.220513.830516.455517.244518.746519.248519.715520.170520.296523.141525.943527.106528.843529.452529.963532.495

4015203040101025

lOOp407

8030804090801550

*90706

507050606050p407090903

607020

1501520

1501251251257068

12530

1506090

15020015060

1259050

12540709080

255924.7255 299.7254940.5254500.8253455.9251873.9250559.4243471.6243562.6243 136.9232567.3225 752.3220453.9219094.1218008.6217 132.0216915.5216052.0213412.2212803.6212730.8212 513.7209483.7207 148.6207013.7206 940.5206653.4205917.2205569.3204 678.5204 528.5203793.0203405.7203 333.0203255.0203 115.4202 397.4202 171.7201475.7200784.7200211.8200 186.1199060.0196569.2196379.6196 118.6194 921.5194848.2194617.0193627.6193 332.4192 772.6192586.3192413.1192 244.9192 198.1191153.0190134.8189 715.1189092.2188874.4188692.4187795.3

4p6 lSo-4d 3p;

4d 3P1 -4f 1/2[5/2]24d 3p - 4f 1/2 [5/2]34d 3P; -4f 3/2[3/2]24d 3P1-4f 3/2[3/2]14d 3F'-4f 1/2[7/2]44d 3P; - 4f 3/2 [5/2]24d 3P;-4f 3/2[3/2]14d 3pF-4f 3/2[3/2]24d 3FP-4f 1/2[7/2]34d 3P1-4f 3/2[5/2]34d 3P1-4f 3/2[5/2]24d 3P1-4f 3/2[3/2]14d 3FP-4f 3/2[5/2]34d 3FP-4f 3/2[7/2]44d 3F'-4f 3/2[5/2]34d 3F' - 4f 3/2 [5/2]24d 3F'- 4/ 3/2 [3/2]24d 3D'-4f 1/2[7/2]44d ID1-4f 1/2[5/2]24d 3F'- 4f 3/2 [7/2]44d 3D1-4f 1/2[5/2]24d 3F-4f 3/24[7/2134d 3F2-4f 3/2[5/2]34d 3F; - 4f 3/2 [5/2124d 3F4-4f 3/2[9/2] 44d 3F2 - 4f 3/2 [3/2]14d 3F'-4f 3/2[9/2]54d 3pD-4s4p64d 1D24d 3D'-4f 1/2[5/2]24d 3F-4f 3/2p[9/2144d IDI-4f 1/2[7/2]34d 3F' -4f 3/2[7/2]34d 3D'-4f 1/2[5/2134d 'P1-4f 1/2[5/2]34d 3F' - 4s4p6 4d ID24d 3D-4f 1/24[7/234d 3DI-4f 3/2[5/2]34d 3DI-4f 3/2[5/2]24d IF -4f 1/2 [7/2]44d IF -4f 1/2 [7/2]34d 3P;-4s4p 6 4d 3D,4d 3FP-4s4p 6 4d 1D

4d 3DI-4f 3/2[7/2]44d 3D; -4f 3/2 [3/2]2

4d 3P;-4s4p 6 4d 3D4d 3P'-4s4p64d33D4d ID -4f 3/2 [5/2]24d 3p;-4s4p64d 3D34d 3D; -4f 3/2 [5/2]24d 3D;1 - 4f 3/2 [3/2114d 3DI-4f 3/2[9/2] 44d 3PI-4s4p 6 4d 3D

534.802535.133536.498537.310537.521538.087538.153542.629543.704544.598549.432551.609556.873560.121560.543563.717563.844569.864574.280578.069581.952583.380589.559591.914592.379592.946595.426599.343601.229604.893605.336606.536609.187613.074613.411621.862622.929623.769623.988625.525628.428630.463632.869635.368638.867

639.560639.606639.688640.122641.196645.500648.389649.574650.066650.283650.427650.821652.177652.647654.513654.710656.020


9040

2001001003080709020

15060

10010060

10010090

150100

2p50504030606060801

10020p

10040

1004090305

209080801550

30lop1549

901550304015106015159015

186 985.2186869.3186394.0186 112.4186039.4185 843.4185 820.8184 288.1183923.5183 621.7182006.3181287.8179574.3178 533.0178398.5177 394.0177 354.0175480.5174131.1172989.8171835.5171414.9169618.2168 929.3168810.9168649.4167 949.0166849.3166 325.9165318.5165 197.4164870.8164153.2163 112.5163022.9160807.4160531.9160315.8160259.6159865.8159127.2158613.6158010.5157 389.1156 527.1

156 357.6156346.1156 326.3156 220.3155958.6154918.7154228.5153946.9153 830.5153 779.1153745.2153652.1153 332.7153222.3152785.5152739.4152434.4

4d 1DI-4f 3/2[7/2]34d 1F -4f 3/2[3/2]24d3F;-4s4p 6 4d3D34d 3D -4f 3/2[5/2]34d 3D2-4f 3/2[5/2]2

4d 3D-4f3/2[3/2]14d 3D;-4s4p 6 4d 1D2

4d3F;-4s4p 6 4d3D34d F'P-4/3/2[5/2]34d 3F;-4s4p 6 4d 3D2

4d IF;-4f 3/2[7/2]44d 1DI-4s4p 6 4d 'D24d3D;-4s4p 6 4d 1D24d 3FP-4s4p 6 4d 3D2

4d 'FP-4f 3/2[9/2]44d3F;-4s4p 64d3Dj4d 3DI-4s4p 6 4d 'D2

4d 'F1-4s4p 6 4d 'D24d 3DI-4s4p 6 4d 3D

5p 3/2[1/2]1-7s 3/2[3/2]4d 1D;-4s4p 6 4d 3D2

5p 3/2[1/2] 1 -7s 3/2[3/2];4dlD;-4s4p6 4d3Dl4d3D; -4s4p 6 4d 3D4d 3DI-4s4p 6 4d 3D3

4d 'FI-4s4p 6 4d 3D35p 3/2[5/2]2-7s 3/2[3/2]15p 1/2[3/2]1-7s 1/2[1/2]15p 3/2[5/2]2-7s 3/2[3/2]1

4d 3P;-5p 1/2[1/2]o4d IF;-4s4p 64d 3D2

5p 3/2[5/2]3-7s 3/2[3/2];5p 3/2[1/2]2-76d3/2[3/2];5p 3/2[1/2]1-6d 3/2[1/2]15p 1/2[3/212-7s 1/2[1/2]15p 3/2[3/2]1-7s 3/2[3/2]1

5p 1/2[1/21,-7s 1/2[1/21l5p 1/2[1/2]1-7s6 /2[1/21]

4d3PI-5p 1/2[1/2]15p 3/2[3/22-7sp3/2[3/2],

5p 3/2 [3/2]2 - 7s3/2 [3/212

5p 3/2 [52122- 6d 3/2 [5/2];

4d 3P - 5p 1/2 [1/2]14d 3P; -5p 1/2 [3/212

Joseph Reader and Nicolo Acquista. 241



(A) sity (cm-') Classification (A) sity (cm-1) Classification

656.159657.387659.143661.055661.702662.324664.250664.635664.857666.467667.409669.703669.954673.340673.686674.034674.134675.342675.526675.865677.663678.056679.394683.536687.576688.268690.520703.026712.488712.855713.053716.978717.236719.739721.323724.454728.741730.188730.430733.148733.413734.941740.331740.613742.181742.736744.018744.753746.913748.538749.810749.977752.020752.484753.160754.582756.107762.852764.578766.200766.388769.567771.180

6060201040103

1060302

302560

1005

2 0 0p30

200151550

3005

40200100200p405040

15030010015060404010603060

2002000

2550050603040309040

30030207070

300500

201520

152402.0152 117.4151712.1151273.4151125.4150983.5150545.7150458.6150408.2150044.9149833.1149319.9149 264.0148513.4148437.1148360.5148338.5148073.0148032.8147 958.6147 566.0147480.4147190.0146 298.0145438.4145292.2144818.4142242.3140353.2140 281.1140242.1139474.3139424.2138939.2138634.1137 792.2137 222.9136951.0136 905.7136 398.1136 348.9136065.3135074.7135023.3134738.0134637.3134437.4134272.8133 884.4133593.8133 367.1133337.4132975.2132893.1132773.9132 523.8132 256.4131087.1130791.2130514.3130482.1129943.2129671.4

5p 3/2[5/2] 2 -6d 3/2[7/2]1

5p 3/2[5/2] 3 -6d 3/2[5/2];

5p 3/2[3/211-6d 3/2[3/2];5p 3/2[5/2] 3 -6d 3/2[7/2];

5p 3/2[5/2]3-6d 3/2[7/2]4

5p 1/2[1/21o-7s 1/2[1/2];

5p 3/2[3/2]1 -6d 3/2[5/2];5s 3/2 [3/2]; - 4f 1/2 [5/212

4d 3 P-5p 1/2[3/2]15p 3/2[1/21o-7s 3/2[3/2];

4d 3 P2-5p 1/2[1/2]1

4d 3 P;- 5p 1/2[3/212

5p 3/2[3/2]1-6d 3/2[1/21;5p 3/2[3/2] 2 -6d 3/2[5/2]3

4d lP;-4f 1/2[5/2125p 3/2 [3/2]2 - 6d 3/2 [3/2]5p 3/2[3/2]2 - 6d 3/2 [1/2];

4d 3 P-5p 3/2[1/2]o

4d 3 F;-5p 1/2[3/212

4d 3P;- 5p 3/2[3/2]14d 3 P; -5p 3/2[3/2124d 3 F;-5p 1/2[1/2]14d 3 F;-5p 1/2[3/212

5s 3/2[3/2]-4f 3/2[3/212

4s4p6 4d 3 D1 -6g 3/2[5/2];4d lP;-4f 3/2[3/2]24d 3 P;-5p 3/2[3/212

4d 3F;-5p 1/2[3/2],

5s 1/2[1/21-4f 1/2[5/2124s4p64d 3 D3 -6g 3/2[7/2]1

4d 3 P;-5p 3/2[5/212

4d 3 P2-5p 3/2[3/21,

4d 3D;-5p 1/2[1/2]o4d 3P;-5p 3/2[5/2134d 3P-5p 3/2[1/2],

773.804775.582779.210783.520784.496785.350785.481795.295796.029797.227797.780800.001800.301801.929803.902806.887808.810809.419809.754812.052812.398812.577813.074816.209821.221822.055822.415823.461823.779825.129825.263828.531830.586836.566841.399849.110851.390852.764852.868853.429853.684855.399858.892859.126862.480862.674863.561867.930869.776873.106873.400877.985884.799885.038885.481885.679886.216887.596888.610889.492890.414895.605897.801


200200200

304008040

100100400

5010000

507060

100008020

20010000

403020

10060

50060

300p200200

4 0 plOu

200400

300030u7090

3 00p60

70020

1001590206040

10020030

1001008030

30030103

80306080

129231.6128935.4128335.1127629.1127470.4127 331.8137 310.5125739.5125623.6125434.7125 347.8124999.8124953.0124699.3124 393.2123933.2123638.5123 545.4123 494.3123 144.8123092.3123064.3122990.0122 517.6121769.9121646.4121593.1121438.7121391.8121193.2121173.5120695.5120396.9119536.3118849.7117770.3117455.0117 265.7117 251.4117 174.3117 139.4116 904.5116429.0116397.3115944.7115918.6115799.6115 216.6114972.1114533.6114495.1113897.2113020.1112989.5112933.0112907.7112839.3112663.9112535.3112423.7112307.3111656.4111383.3

4d 3F3- 5p 3/2[3/2124d 3 P2- 5p 3/2[5/2124d 3P;-5p 3/2[1/2]1

4d 3F:-5p 3/2[5/2]3

4d ID2-5p 1/2[1/2]14d 3F; - 5p 3/2 [3/2124d 'D -5p 1/2[3/212

4d 3F3 - 5p 3/2[5/213

4d3D;-5p 1/2[1/2]1

4d 3P2- 5p 3/2[1/2]1

4d 3F;-5p 3/2[3/2]14d 3F - 5p 3/2[5/212

5s 3/2[3/21l-4s4p 6 4d ID 25s 1/2[1/2]1-4f 3/2[3/212

4d3D -5p 1/2[1/2]1

4d 1D;-5p 1/2[3/2]14d 3F; - 5p 3/2[5/2134d IP;-4s4p 6 4d 'D2

4s4p64d lD2-6g3/2[7/2];4s4p64d 'D 2-6g3/2[5/213

4d 3 D;-5p 1/2[3/2]14d 3F; - 5p 3/2[5/2124d IF;-5p 1/2[3/212

4f 3/2 [9/215 - 6g 3/2 [9/2];

4f3/2[9/2]5-6g 3/2[11/2164d 3D; - 5p 3/2[1/2]o

4s4p6 4d 3D2-5g 1/2[7/2]14d 3 D;- 5p 3/2[3/212

4f3/2[9/2] 4 -6g 3/2[9/21l4f3/2[9/2] 4 -6g 3/2[11/2]15p 3/2[1/2]1-6s 1/2[1/2];4f 1/2 [7/213 -6g 1/2 [9/21:

4s4p64d 3D3-5g 1/2[7/2]:4f 1/2[7/2] 4 -6g 1/2[9/2]5

4d 3F;-5p 3/2[1/211

4f 3/2 [7/2]3 - 6g 3/2 [9/2]44f3/2[7/2] 4 -6g 3/2[9/2]14f1/2[5/2]3-6g 1/2[7/21l

4d 3 D - 5p 3/2[5/2134f3/2[7/2]4-6g 3/2[7/2145s 3/2[3/2]2-4s4p6 4d 3D3

4f3/2[7/2] 4 -6g 3/2[11/2];4d 'D2-5p 3/2[3/212

4d 3D - 5p 3/2[3/212

Joseph Reader and Nicolo Acquista. 242



(A) sity (cm- 1 ) Classification (A) sity (cm-') Classification

900.476904.941905.989906.606906.663907.984908.590915.123915.300915.829923.100924.276924.710932.046932.793933.763936.170936.201940.408941.612943.480944.187944.828945.396949.705960.626974.361978.062978.257980.704982.518984.176986.080986.832990.369990.842995.590997.073998.801

1001.7651002.4841005.6331009.5601028.3801038.6901044.4071045.779

1047.7741048.9701051.3291058.6191066.4861068.5511069.2201072.2471081.1421081.4121083.4521085.4581087.0471093.1001093.537

300100509Op

500601560

50060

40010010808030

10070

4001508070

15050p

20015030

20070

20040

2004080

15040

30015030

150400

3015

10040020030

30020605

5040030

3006060

30020p

20090

200

111052.4110504.4110388.8110301.4110294.6110 134.1110060.6109274.9109253.8109 190.7108330.6108192.8108142.0107 290.8107 204.9107093.5106 818.2106814.6106 336.8106 200.9105990.5105911.3105839.4105775.8105295.8104098.8102631.4102 243.0102222.6101967.6101779.3101607.8101411.6101334.3100972.5100924.3100443.0100293.6100120.099823.7799752.2299439.8699053.1197 240.3096275.0895748.1095622.50

95440.4195331.5795117.7494462.7193765.8693584.6993526.1693262.1092494.7692471.7392297.6092126.9691992.3691482.9791446.39

4d 3 D -5p 3/2[5/2]24f3/2[5/2]3-6g 3/2[7/2]4

4f3/2[3/2] 1 -6g 3/2[5/2]4d 1D;-5p 3/2[3/2],

4f3/2[5/2J 2 -6g 3/2[5/2]f4/ 3/2[5/2] 3 -6g 3/2[5/2];

4d 3D;-5p 3/2[3/2]1

4d 3 D2- 5p 3/2[3/2124d 1D;-5p 3/2[5/2]3

5s 3/2 [3/21]- 4s4p 6 4d 3D24/ 3/2[3/2] 2 -6g 3/2[7/2];

4d 1PI-4s4p64d3D2

4d 'D2-5p 3/2[5/2124d 3 D;- 5p 3/2 [3/2]1

4d 'F -5p 3/2[3/2124d 1Pl-4s4p64d 3Dj4d 3 D; - 5p 3/2[5/2124d 3 D-5p 3/2[5/2]3

4d 3 D2- 5p 3/215/212

4s4p64d 3D1 -5g 3/2[5/2]24s4p64d 3D2 -5g 3/2[7/2];

4d 'F -5p 3/2[5/213

4d ID 2 -5p 3/2[1/2]14s4p64d 3D2 -5g 3/2[5/2];4s4p64d 3D2 - 5g 3/2 [5/2] 25p 3/2[1/21 1 -6s 3/2[3/2];

4d 3 D;-5p 3/211/2]15p 3/2[1/2] 1 -5d 1/2[3/2];

4s4p 64d 3 D3 -5g 3/2[7/2]44d 'F -5p 3/2[5/212

5p 3/2[1/2]o-6s 1/2[1/2]f4s4p 6 4d 3 D3 - 5g 3/215/2]1

4d 3 D;-5p 3/2[1/2]5p 3/2 [5/2]2 - 6s 3/2 [3/2];5p 1/2[3/2] 1 -6s 1/2[1/2]o

J5p 3/2 [3/2]1- 5d 1/2 [3/2]15p 3/215/12] 2 -5d 1/2[5/2f35p 3/2[5/212-6s 3/2[3/2]14/ 3/2[7/2]3-5g 1/2[9/2]:5p 3/2[5/2] 2 -5d 1/2[3/2]J4/ 3/2[7/2]4 -5g 1/2[9/2];5p 3/2[5/2] 3 -5d 1/2[5/2];5p 3/2[5/2]3-6s 3/2[3/2];

5p 3/2[5/2] 3 -5d 1/2[3/2];

5p 1/2 [3/2]2 -6s 1/2 [1/2] I4/ 3/2[5/2J3 -5g 1/2[7/2]J5p 1/2[1/2]1-6s 1/2[1/2],5p 3/2[3/2]1-6s 3/2[3/2125p 1/2[1/2]1-6s 1/2[1/2]o

1101.5021105.5661108.7941114.6881115.5331116.8781118.6931123.2051130.1521131.9141132.2301132.3771134.6121141.2231142.5521144.0891144.5831145.4471154.7611166.6031168.1631183.7341185.9651188.5561194.2401200.7611200.9381212.9351217.9571227.7201232.5571233.9111238.9271245.9521247.2481253.6071259.6961260.9141262.9621265.3801270.1191295.8091298.5761300.7701301.3211302.0271302.8041303.1951303.9331306.7641312.2471315.142

1315.4421315.9971316.4141320.7451323.8131327.8221332.0631337.3381340.4231342.525


3040

200609020705070705

6015

10050

1501520

10010015080

55

30030060

loop90

loop10020030015030

30020040010050080

30090

1507080

400loop50040060

200

100106

4005 0 0 p1503003003030

90785.1490451.4290188.0689711.2289643.2789535.3289390.0289030.9588483.7188345.9488321.2888309.7888135.8787 625.3087523.4087405.7687368.0587 302.1886598.0485718.9785604.4784478.4584319.4984135.7283 735.2483 280.5583 268.2782444.6782 104.7181451.7881132.1381043.1380715.0180259.9180176.5079769.8079384.2379307.5479179.0779027.6478732.7977 171.8877007.4476877.5576844.9976803.3276757.5176734.4976691.0376524.8976205.1776037.42

76020.0875988.0275963.9475714.8675539.3875311.3275071.5574775.3974603.2974486.53

5p 3/2[3/2] 1-5d 1/2[5/2]15p 3/2[3/212-6s 3/2[3/211

5p 3/2[3/2] 2-5d 1/2[5/2]3

5p 3/2[3/2] 2 -5d 1/2[3/211

5p 3/2[3/2] 2-5d 1/2[5/2];

5p 3/2[1/2]o-5d 1/2[3/211

4s4p6 4d 'D 2 -5g 3/2[7/2]3

4s4p64d 1D2 - 5g 3/2[5/2]15p 3/2[1/2] 1 -5d 3/2[5/2115p 1/2[1/2]o-6s 1/2[1/2]15p 1/2[3/2]1 -5d 1/2[3/2];5p 3/2[1/21o-6s 3/2[3/2114/ 3/2[9/21 5-Sg 3/2[9/2]15p 3/2[1/21 1 -5d 3/2[3/2]14/3/2[9/2]s-5g 3/2[11/2]14/3/2[9/2]4-5g 3/2[9/2]14/3/2[9/2]4-5g 3/2[11/2)14/ 1/2[7/2]3-5g 1/2[9/2]:5p 3/2[3/21 1-5d 3/2[3/2]14/ 1/2[7/2] 4 - g 1/2[9/2];5p 3/2[1/2] - 5d 3/2[1/21]5p 3/2[5/21 2 -5d 3/215/2114/ 3/2[7/213- g 3/2[9/2]:5p 1/2[1/2]1 -5d 1/2[3/2];5p 3/2[5/2] 3 -5d 3/2[5/2114/ 3/2 [7/2]4 - 5g 3/2 [9/2]5p 1/2[3/2] 1 -5d 1/215/2114/ 1/2 [5/2]3 - 5g 1/2 [7/2]15p 3/2[5/21 2 -5d 3/2[7/21;5p 3/2[5/2] 2 -5d 3/2[3/2115p 3/2[5/2] 3 -5d 3/2[7/2]15p 3/2[5/2]2 - 5d 3/2[1/2];5p 3/2[5/2] 3 -5d 3/2[3/2]14/ 3/2[5/212-5g 3/2[7/2]14/ 1/2[5/212 - 5g 1/2[7/2];5p 3/2[3/2]1 -5d 3/2[5/2]14/ 3/2[5/2]3- g 3/2[7/2]15p 3/2[5/21 3 -5d 3/2[7/2]15p 1/2[3/2] 2 -5d 1/2[5/2];4/ 3/2[3/2] 1-5g 3/21[5/2]I5p 1/2[1/2]i-6s 3/2[3/1214f3/2[5/2] 2 -5g 3/2[5/2]15p 1/2[3/2] 2 -5d 1/2[3/2]14/ 3/2[5/212- g 3/2[5/2]14/ 3/2[5/2]3- g 3/2[5/2135p 1/2[1/2] 1 -5d 1/2[3/2]15p 3/2 [3/2]2 - 5d 3/2[5/2]15p 1/2[3/2] 2 -5d 1/2[5/2]15s 3/2[3/2];-5p 1/2[1/21o5p 3/2 [3/2] 1 - 5d 3/2 [3/2]2




(A) sity (cm-') Classification (A) sity (cm-') Classification

1352.0531355.2141355.9751360.1041361.3871370.9861373.3441375.2121376.5421384.3891387.2861396.7911400.3351401.8381408.8441409.8361410.0321411.3281413.4001419.9181430.1561437.1201447.4871451.9481460.0461462.4781484.5701486.9031491.3281506.1871509.4201517.6161520.4711533.2181534.7231537.2191547.3891550.1241551.9941559.2841575.631

5030050070

3002

9080

5002030

20050909080

30030

2006030606090

3008060

3003001006090

20050

1503070

200407040

73961.5773789.0973747.6773523.8073454.4872940.1872814.9672716.0672645.8072236.1172083.2171592.6671411.5071334.9170980.1870930.2370920.3870855.2370751.3770426.5869922.4269583.5969087.2668872.9868491.0068377.1067 359.5667253.8767054.3366392.8166250.6265892.8365769.0765 222.3065158.3365052.5564624.9964510.9564433.2664131.9863466.65

5p 1/2[1/2]o-5d 1/2[3/2];4d 'P;-5p 1/2[1/2]o

4f3/2[3/2] 2 -5g 3/2[7/2]35p 3/2[1/2]o-5d 3/2[3/2];5p 3/2 [3/212 - 5d 3/2 [7/21]

4/ 3/2[3/2] 2 -5g 3/2[5/2]35p 3/2[3/2] 2 -5d 3/2[3/2];

5p 3/2[3/2] - 5d 3/2[1/21o

5s 3/213/21]- 5p 1/2[3/212

5p 3/2[3/2] 2 -5d 3/2[1/2];

5s 3/2[3/2]1-5p 1/2[3/2124d 1P;-5p 1/2[1/2]1

4d 1P-5p 1/2[3/2]2

4/ 1/2[7/2] 4 - g 3/2[11/2];

5p 3/2[1/2]o- 5d 3/2[1/2];

1585.8531591.8011603.7741633.0261645.3361654.4581676.8421682.2551725.0151735.9471750.4331765.5781767.7911772.0841786.1971790.8121806.0911860.4831860.8641874.3861878.3331926.2361927.4271934.8762009.9412029.1932085.2042133.0942145.5872150.8602221.8672234.7392337.6602420.6892429.2852451.2162454.6262473.9252617.5422646.2432675.190

erence spectra and unknown spectra, we used impurity linesof oxygen, nitrogen, carbon, and silicon."11

The wavelengths, intensities, and classifications of theobserved lines of Zrv are given in Table I. The intensities arevisual estimates of photographic plate blackening. For un-perturbed lines the uncertainty of the wavelengths is esti-mated as +0.005 A. Included in Table I are several linesbelow 174 A given in Ref. 2 that we did not remeasure. Of the577 observed lines, 330 are classified.

ANALYSIS OF SPECTRUM

The analysis was begun by using the known J = 1 levels ofthe 4p5(4d + 5s) and 4p5(5d + 6s) configurations to developlevels having J = 0, 1, 2 of the 4p 5 5p configuration. These4 p55p levels were then used to extend the 4p5(4d + 5s) and


4p5(5d + 6s) levels to further J values. Continuing in thisway, all levels of the 4p 5 (4d + 5s), 4p 5 5p, 4p 5 (5d + 6s) con-figurations and most of the levels of 4p 5 (6d + 7s) were locat-ed.

The location of these levels was greatly aided by ab initiocalculations of the structures of the configurations. Thecalculations were carried out by diagonalizing the energymatrices with Hartree-Fock (HF) parameters obtained fromthe computer code of Froese-Fischer.1 2 Scaling factors forthe HF parameters were taken from analyses of the isoelec-tronic atoms Rbii, 1 3,14 Sr 11,15 and YIV.16 (The matrices forthese configurations as well as those that follow were calcu-lated in an SL-scheme with the Fano-Racah phase convention.The electrons were ordered as sMpNl.)

Locating the levels of the 4p5 4 f configuration was some-what more difficult. The 4p54f configuration interacts


9010060

50040

5002050

7008

205

3040

5002 0 0p50050060050

50040050040050060010060030

2008020

2008080356030303010

63057.5562821.9362352.9461236.0360777.8660442.7659635.9059444.0357970.5257605.4557406.9356638.6856567.7856430.7355984.8755840.5955368.1953749.4853738.4753350.7953238.7051914.7251882.6351682.9049752.7049280.6747956.9546880.2546607.2946493.0245007.1744747.9542777.8141310.5541164.3840796.0940739.4140421.6038203.7937789.4337 380.52

4d 1P;-5p 1/2[3/2]1,

5s 3/2[3/211-5p 3/211/21o

5s 1/2[1/2];-5p 1/2[1/2]o5p 1/2[3/2] 2 -5d 3/2[3/2]2

5s 3/2[3/21]-5p 3/2[3/2125p 1/2[1/2]-5d3/2[1/2]j

5p 1/2[1/2fl-5d 3/2[1/212

5s 1/2[1/21-5p 1/2[1/2]15s 3/2[3/212 - 5p 3/2[3/2]15s 3/2[3/21-5p 3/2[3/2125s 1/2[1/211-5p 1/2[3/2125s 3/2[3/21-5p 3/2[5/2]3

5s 3/2[3/2]f-5p 3/2[3/2]24d 1P;-5p 3/2[3/212

5s 3/2 [3/212-5p 3/2[5/2]25s 1/2[1/21l-5p 1/2[3/2]15s 1/2[1/21]-5p 1/2[3/2125s 3/2 [3/2];- 5p 3/2 [5/212

4d 1P - 5p 3/2 [5/2125s 3/2 [3/2]2 - 5p 3/2 [1/2]115s 1/2 [1/2];- 5p 3/2 [1/21]o

5s 1/2 [1/2 l- 5p 3/2 [3212]

TABLE 11. Energy levels of Zrv.

Configuration Term J E(cm-1) Unc. (cm-') Configuration Term J E(cm-l) Unc. (cm-1)

4p6 iS

4p 5 4d 3po3p0

3po

3Fo3Fo3F0

3D°1D'3D'3D°

lpo

4p55s 3/2[3/2]°3/2[3/2] 01/2[1/2]°1/2 [1/2] 0

4 p 5 5p 3/2[1/2]3/2[5/2]3/2[5/2]3/2[3/2]3/2[3/2]3/2[1/2]1/2[3/2]1/2[3/2]1/2[1/2]1/2[1/2]

4s4p 64d 3D3D3DID

4 p54f 3/2[9/2]3/2[9/2]3/2[7/2]3/2[7/2]3/2[3/2]3/2[5/2]3/2[5/2]3/2[3/2]1/2[7/2]1/2[7/2]1/2[5/2]1/2[5/2]

4p55d 3/2[1/2]13/2[1/2]°3/2[7/21]3/2[3/2]03/217/2]°3/2[5/2]°3/2[5/21]3/2[3/2]°1/2[5/2]°

0 0.0 1.9

0 241381.31 243 560.82 247962.34 251283.33 253 753.42 257361.33 265845.52 270560.81 271601.62 274654.63 277145.51 328940.75

2 325014.871 327616.990 340315.491 342 245.65

1 371895.162 376897.683 378753.361 380855.532 382985.080 388852.951 391998.412 395994.981 396300.350 402688.40

1 434714.62 435759.13 437678.12 450133.7

5 453680.84 454538.83 457546.74 458432.21 460476.92 460694.13 460767.52 464015.43 470773.54 471762.43 473715.42 476130.2

0 452938.911 453905.604 455444.42 455630.83 455925.272 457613.13 458523.71 462307.42 471306.3

0.60.40.30.70.40.30.40.20.20.20.30.09

0.100.120.130.07

0.120.090.120.110.080.100.100.130.110.14

0.50.30.30.3

0.70.40.40.30.40.20.30.20.50.50.60.4

0.190.160.30.140.180.30.60.30.2

1/2[3/2] °1/2[5/2]°1/2[3/2]°

4p56s 3/2[3/2]°3/2[3/2]°1/2[1/2]°1/2[1/21]

4p56d 3/2[1/2]13/2[7/2]°3/2[3/2]13/2[7/2]13/2[5/2]°3/2[5/2103/2[3/2]01/2[3/2]°

4p57s 3/2[3/2]13/2[3/2]°1/2[1/2101/2[1/2]0

4p55g 3/2[5/2]03/2[5/2]°3/2[11/2]°3/2[11/2]°3/2[7/21]3/2[7/21]3/2[9/2]°3/2[9/2]o1/2[9/2]°1/2[7/21]1/2[9/2] 01/2[7/210

4p56g 3/2[5/2]°3/2[5/2] 0

3/2[11/2]03/2[11/2]03/2[7/2]03/2[7/2] °3/2[9/2] 03/2[9/2]01/2[9/211/2[7/2]01/2[9/2] 0

4p57d 3/2[3/2]°1/2[3/2]0

4p58s 3/2[3/2]°1/2[1/2]o

4s4p 6 5p 1PO

4p 59s 3/2[3/210

4p5 10s 3/2[3/2]°


472015.28472520.0476477.4

472 338.0473 172.7487 746.6488 292.7

528422.8529161.6529283.3529 299.6530 119.7530465.5531839.0546323

536 763.9537 213.4552 258.2552521.1

536 682.2536731.5536961.4536 983.9537 501.9537 539.2537 806.7537816.5552878.2552894.5552894.7552933.5

570779.3570828.2570946.5570967.6571271.7571306.3571443.6571452.2586704.9586 718.2586734.5

1 5680401 583420

1 5713761 586882

1 573776

1 591916

1 605118

0.190.30.3

0.20.30.30.2

1.01.11.01.10.80.81.1

15

0.70.61.20.9

0.30.20.80.80.50.20.40.40.50.50.40.5

1.00.51.00.50.40.60.60.70.80.80.8

1617

1617

17

18

18


strongly with the 4s4p6 4d configuration, and the level pre-dictions for both configurations are thus sensitive to theirestimated relative positions. In Srii the 4s4p6 4d configu-ration lies well above the ionization limit and is not observed.Nevertheless, considerable information about the4s 2 4p 5 4f-4s4p 6 4d interaction can be inferred 15 from theobserved level distortions within 4p54f. In YIV16 the 4s4p 6 4dconfiguration lies well below the limit, and all of its levels areknown. The Y IV spectrum thus provides information aboutthe parameters to be used within each configuration as wellas between the two interacting configurations.

For our ab initio calculation the energy of the 4p5 4f con-figuration relative to the ground state was estimated by ex-trapolating the positions of the J = 4 and J = 5 levels in theisoelectronic sequence to Zr v. These levels are not perturbedby levels of 4s4p 64d and thus can be used to provide a reliableestimate of the unperturbed position of 4p5 4f. The resultantaverage energy of 4p5 4f was 460000 cm- 1. The energy of the4s4p 6 4d configuration was estimated by assuming that it liesbelow the 4s4p 6 configuration of ZrVI by an amount equal tothe term value of the 4d configuration of Nb v. (This is themethod used by Hansen and Persson'5 to estimate the posi-tion of 4s4p 6 4d in Sr III; it is the same method used by Reader,Epstein, and Ekberg2 to predict the positions of the 4s4p6 5pconfigurations for several ions in the KrI isoelectronic se-quence.) The energy relative to the ground state thus ob-tained, 432000 cm'1, was corrected to 442000 cm-' on thebasis of similar calculations for the 4s4p 6 4d configuration ofYiv and the 4s4p6 5p configuration of Zrv. The level posi-tions were calculated by diagonalizing the complete 4s 2 4p 5 4f+ 4s4p 6 4d energy matrix. By using these calculated positionsas a guide, all of the levels of these two configurations werelocated.

The analysis of the spectrum was completed with the ad-dition of the 4p 5 5g and 6g configurations. At this stage of theanalysis about 250 lines of Zrv, most of them lying at shortwavelengths, remain unclassified. These lines probablyrepresent transitions to complex configurations having furthervacancies in the 4s and 4p shells. (For example, transitionsof the type 4s24p5 4d-4s2 4p4 4d2 are expected to be at about300 A.) The analysis of such complex configurations is be-yond the scope of this work.

The list of observed energy levels is given in Table II. Thevalues of the levels were determined by a least-squares opti-mization procedure that uses all of the measured wave num-bers.17 The uncertainties of the level values given by thisprocedure are also listed. Uncertainties greater than 0.2 cm-have been rounded to the nearest 0.1 cm-', with a corre-sponding rounding of the level values. The levels are desig-nated in either LS or Jl coupling.

compositions given in Table III show that the coupling within4p 5 4d is far from being pure in either the LS or J11 scheme.However, the coupling in 4p65s is nearly pure J 1.

As shown in Fig. 1, the 4p5 4d 'P1 and 4p 5 5s 3/2[3/2]1 levelsare very close in energy. (The designations of these levels areconfirmed by the intensities of transitions between these levelsand levels of the 4p5 4f and 4s4p6 4d configurations.) It istherefore puzzling that, although both levels contain appre-ciable 1P character, the isoelectronic diagram for these levelsin Ref. 2 shows no noticeable perturbation at Zrv. Indeed,our calculations show that these two levels have unperturbedpositions that nearly coincide. That they remain so close isundoubtedly due to a relatively small overlap of the 4d and5s wave functions. This can be seen by comparing the 4p 5(4d+ 5s) parameters through the isoelectronic sequence.13 -16

Although the electrostatic parameters withiin the configura-tions increase nearly linearly with Z,, the net charge of theatomic core, the configuration interaction parameters decreaseslowly through the sequence. Thus, on a relative basis, con-figuration interaction becomes considerably smaller as thesequence progresses, which merely reflects the tendencytoward hydrogenic orbitals with increasing Z,. The ad-mixture of configuration states in Zrv is about 14%.

Inasmuch as only two levels of 4p5(4d + 5s) are significantlyaffected by configuration interaction, it was not possible toallow both configuration interaction parameters to remain freein the least-squares fit. R1 (4p4d,5s4p) was thus held at itsHF ratio to R2 (4p4d,4p5s) in the calculations. Although thefitted value of R2(4p4d,4p5s) is low compared to the HFvalue, the small value (0.22) of the cancellation factor asso-

320

EU000

CD

zwr 2801

DISCUSSION AND THEORETICALINTERPRETATION

4p5 (4d + 5s) configurationsThe 4p5(4d + 5s) levels are plotted in Fig. 1. The results

of fitting the energy parameters to the observed levels by aleast-squares calculation are given in Table III. The fittedvalues of the parameters, along with the HF values and thefitted/HF ratios, are given in Table IV. The percentage


240

0 I 2J VALUE

3 4

FIG. 1. Structure of the 4p54dand 4p 5 5s levels of Zrv. Heavy lines,4p54&d dashed lines, 4p55s. The levels of 4p5 5s are designated in J11coupling.


I I I I I

-I[ a]---

'P

-- -- [--

4p5 (4d + 5s)

3 D D = \

D3 \

-3P

pI I I

TABLE 1ll. Calculated energy level values in cm- and percentage compositions for the 4p5(4d + 5s) configurations of Zrv. States of 4p5 5s are denotedby an asterisk. Negative eigenvector components are preceded by a minus sign.

PercentageJ E(obs.) E(calc.) obs.-calc. % Ji1 composition-LS

0 241381 241499 -118 100% 3/2[1/2] -100% 3P340315 340315 0 100% 1/2[1/2]* 100% 3P*

1 243561 243637 -76 67% 3/2[1/2] -98% 3P - 2% 3D271602 271353 249 49% 1/2[3/2] 97% 3D - 2% 3 P - 1% lp327 617 327 616 1 84% 3/2[3/2] * -45% lp* + 41% 3P* + 14% 'P328941 328944 -3 37% 1/2[3/2] 85% 'P - 8% 3 P* + 6% lP* + 1% 3D342246 342247 -1 97% 1/2[1/2]* -51% 3P* - 49% lp*

2 247962 247983 -21 78% 3/2[3/2] 92% 3P + 6% 3D + 2% 1D257361 257315 46 73% 3/2[5/2] -74% 3F + 15% 1D - 11% 3D270561 270805 -244 73% 1/2[5/2] 47% 1D - 27% 3D + 26% 3F274655 274738 -83 78% 1/2[3/21 -56% 3D - 36% 1D + 8% 3P325015 325016 -1 100% 3/2[3/21* -100% 3P*

3 253 753 253 551 202 68% 3/2[7/2] 87% 3F - 8% 'F + 5% 3D265846 266079 -233 79% 3/2[5/2] 66% 3D + 34% 'F277 146 277 036 110 87% 1/2[5/2] -58% 1F + 29% 3D - 13% 3F

4 251283 251114 169 100% 3/2[7/2] 100% 3F

ciated with this parameter (see Table IV) indicates that theHF value may not be reliable.

4p5 5p configurationThe levels of the 4p5 5p configuration are plotted in Fig. 2.

The percentage compositions are given in Table V; the energyparameters in Table IV. The coupling is fairly pure in the J 11scheme.

4p5(5d + 6s) configurationsThe levels of the 4p5(5d + 6s) configurations are plotted

in Fig. 3. The percentage compostions are given in Table VI;the energy parameters in Table IV.

Again there is a near coincidence of levels having the sameJ value, in this case 4p5 5d l/2[3/212 and 4p56s3/2[3/2]2.Configuration interaction is possible for these two close levelsbecause they both contain significant amounts of 3P character.However the configuration interaction integrals are again verysmall and, in fact, there is not much interaction. The ad-mixture of states amounts to only about 4%. As shown inTable IV the configuration interaction parameters could notbe well defined in the least-squares fit.

4p5 4f + 4s4p 6 4d configurationsThe levels of the 4p5 4f + 4s4p 6 4d configurations are

plotted in Fig. 4. As can be seen, the entire 4s4p 6 4d config-uration lies below 4p5 4f, which is the first instance that thisoccurs in the isoelectronic sequence. In our least-squares fitfor these levels we neglected interactions between 4s4p 64dand higher 4 p5 nf configurations, although according to ourab initio calculations these interactions are not completelynegligible. We estimate that their neglect results in a fittedvalue of Eav(4s4p 6 4d) that is too low by about 2000 cm- 1 .The results of the least-squares fit are given in Tables IV and


VII. As noted in Table IV, the value of t4f in the least-squaresfit was fixed at the value of t4f observed in the neighboringsingle-valence-electron atom, Nb v.

As already mentioned, configuration interaction (CI) ishighly significant for the 4p54f and 4s4p6 4d levels. Thedistortions of these configurations due to CI can be seen bycomparing the observed levels with their unperturbed posi-tions, shown in Fig. 5. The unperturbed positions representthe levels obtained by diagonalizing the energy matrix withthe fitted values of the parameters, CI being omitted. Thedistortions observed here are similar to those observed in theargon-like ion CaIII by Hansen, Persson, and Borgstrbm.18

Also indicated in Fig. 5 is the distribution of 1"3D characteramong the unperturbed levels. The unperturbed 4s4p 64dlevels are essentially pure ID and 3D states. With these 13D

percentages in mind the effects of CI can be visualized readily.In this connection it should be noted that because of a can-cellation that occurs in the 1D-1D matrix element, the 3D-3Dinteraction between these configurations is inherently largerthan the 1D-1D interaction. (The 3D-3D matrix element is-V5 R1(4p4d,4s4f)/5; the 1D-1D element is v5[-R1(4p4d,4s4f) + 6R2 (4p4d,4f4s)/5]/5.)

Although the J = 2 levels of 4p5 4f at 460 694 and 464 015cm-' have been designated according to their major compo-nents in J1l coupling, the low percentages for these compo-nents indicate that these designations have only limitedphysical significance. Indeed, according to these designationsthese J = 2 levels are reversed from their normal order in p 5 fconfigurations. This apparent reversal of order is due to CI,which mixes different Jl states into the p 5f levels. As shownin Fig. 5, the unperturbed levels do have a normal ordering.The lowest unperturbed J = 2 level of 4p 54f has a majorcomponent of 75% 3/2[5/2]. For isoelectronic comparisonsthe unperturbed levels are probably to be preferred.


TABLE IV. Energy parameters in cm- and mean errors A of least-squares fits for Zr v.

Configuration Parameter HF Fitted Fitted/HF

2584356571481768504229007

620

3308397500 (0.40)a9302

-7023 (-0.22)190 (0.005)

380074221514481 (0.20)6098 (0.60)93631674

453723159019462 (0.75)6790 (0.90)9356

154

4705952357 (0.36)9380

264395 + 6955869 + 61560622 + 36343933 ± 11449633 + 179

652 + 75

331289 +7066 +

10200 +

0.8500.7410.871.071.05

0.941.10

171895205

-2039 + 20015 5 b

218

384586 +21060 +4121 +5910 +

10219 +2242 +

72

462027 +13835 +9293 +6110 +

10256 +207 +

477815 +2 103 ±

10301 +

518 (0.06)1373 (0.16)

295c782 +

41

4588542533815451102159345

4

46383060448

636

2912547899

5316794758

392276

94210.3

461077 +24 265 +14266 +8315 +

10 143 +36d

0.29

0.9510.9200.971.0911.34

0.8700.9820.901.0961.34

0.891.098

0.57

2419820

3263845

1214658

2411913

2314230

447

63840808

111275

447232 + 19023028 + 1432

566 + 111

9446 + 71027962 + 199

139

542489 +4277 +

286 +108 +t

10385 +Oe

8

22833563

0.960.920.811.085

0.380.89

0.320.584

0.899.73.39

1.1023


4p 54d EavF2(4p4d)G'(4p4d)G3 (4p4d)

*4pt4d

4p 5 5s

ConfigurationInteraction

4p5 5p

4p55d

4p5 6s


EavG'(4p5s)t4p

R2(4p4d,4p5s)R1(4p4d,5s4p)

A

Ea,F 2(4p5p)G°(4p5p)G2 (4p5p)t4pt5pA

F 2(4p5d)Gl(4p5d)G3 (4p5d)t4pA5d

EavG 1(4p 6s)t4p

R2(4p5d,4p6s)R'(4p5d,6s4p)

4 p 5 4f EavF2(4p4f)G2 (4p4f)G4(4p4f)*4p-4f

EavG2(4s4d)

t4d

4s4p64d


R2 (4p4d,4f4s)R1 (4p4d,4s4f)

A

4p5 5g EavF2 (4p5g)G3 (4p5g)G5 (4p5g)

t4p*5gA


TABLE IV. (Continued)

Configuration Parameters HF Fitted Fitted/HF

4p 5 6d Eav 542640 534855± 15F 2(4p6d) 6941 6195 142 0.89GI(4p6d) 3679 3402 45 0.925G3(4p6d) 2769 2476 : 241 0.89t4p 9393 10 325ft6d 74 115 ± 13 1.55

4p 5 7s Eav 532684 542098± 17G1(4p7s) 1095 (0.34) 1014 ± 94 0.93t4p 9402 10335 19 1.098

Configuration R 2 (4p6d,4p7s) 768 7689Interaction R1(4p6d,7s4p) 715 7159

A 33

4p 5 6g Eav 564519 576338 + 2F 2 (4p6g) 2786 2513 + 23 0.902G3(4p6g) 372 286 ± 34 0.77G5(4p6g) 263 167 + 49 0.63t4p 9421 10383 + 3 1.1021t6g 0.2 OeA 7

a Values in parentheses are the ratio of the calculated parameter to a value calculated by using the absolute value of each wave function.b Fixed at HF ratio to R2 (4p4d,4p5s).c Fixed at HF ratio to R1(4p5d,6s4p).d Fixed at value of q4f in Nbv.e Fixed at zero.f Fixed at HF ratio to t4p(4p

57s).

g Fixed at HF value.

400 f-

390

3801-

3700 I 2 3

J VALUE

FIG. 2. Structure in the 4p55p configuration of Zrv. The levels aredesignated in J /coupling.


490

.E000CD

wzW

4701-

4500 I 2 3 4

J VALUE

FIG. 3. Structure of the 4p5 5d and 4p5 6s levels of Zrv. Heavy lines,4p5 5d; dashed lines, 4p56s. The levels are designated in J1/coupling.


0E00CDw

zwr

I I I I

2 [] 4p 5 5p

3 [2]

'f 1!

I I [ 2]I I I I 2

I I i rd I I

4p5 (5d + 6s)

2 [2]

3 I I Il

2~ L2J1

lI l 2

TABLE V. Calculated energy level values and percentage compositions for the 4p5 5p configuration of Zrv. Negative eigenvector components are precededby a minus sign.

J E (obs.) E (calc.) obs.-calc. % Jll Percentage composition-LS

0 388853 388812 41 78% 3/2[1/2] 79% 3 P - 21% 'S402688 402699 -11 78% 1/2[1/2] 79% IS + 21% 3 P

1 371895 371929 -34 91% 3/2[1/2] 85% 3S + 14% 3P380856 380949 -93 94% 3/2[3/21 46% lP - 31% 3D - 20% 3 P + 3% 3 S391998 3919.78 20 92% 1/2[3/2] 64% 3D + 33% 'P - 2% 3 P396300 396300 0 89% 1/2[1/2] -64% 3 P - 20% lP + 12% 3S + 4% 3D

2 376898 376857 41 87% 3/2[5/23 58% 3D - 34% ID + 8% 3P382985 383012 -27 87% 3/2[3/2] 68% 3 P + 31% 'D + 1% 3D395995 396010 -15 99% 1/2[3/2] -40% 3D - 35% ID + 25% 3P

3 378753 378674 79 100% 3/2[5/2] 100% 3D

TABLE VI. Calculated energy level values in cm' and percentage compositions for the 4p5(5d+ 6s) configurations of Zrv. States of 4p56s are denotedby an asterisk. Negative eigenvector components are preceded by a minus sign.

J E (obs.) E (calc.) obs.-calc. % Jil Percentage composition-LS

0 452939 452940 -1 100% 3/2[1/2] 100% 3 P487747 487766 -19 100% 1/2[1/2]* 100% 3P*

1 453906 453898 8 67% 3/2[1/2] -90% 3P - 10% 3D462307 462273 34 66% 3/2[3/2] 57% 3D - 39% 1P - 4% 3P473173 473184 -11 98% 3/2[3/2]* -62% 'P* + 37% 3p* + 1% 3D476477 476500 -23 91% 1/2[3/2] 60% 1P + 33% 3D - 6% 3P - 1% 3P*488293 488273 20 100% 1/2[1/2]* -62% 3P* - 38% 1P*

2 455631 455643 -12 96% 3/2[3/2] 66% 3P + 24% 3D + 9% ID457613 457621 -8 98% 3/2[5/2] 45% ID - 31% 3F - 23% 3D471306 471262 44 97% 1/2[5/2] -67% 3F - 25% 'D + 8% 3D472015 472071 -56 92% 1/2[3/2] -43% 3D + 31% 3 P - 21% 'D + 4% 3 P*472338 472324 14 96% 3/2[3/21* 96% 3P* + 2% 3D - 1% 3P + 1% ID

3 455925 455956 -31 91% 3/2[7/2] 61% 3F - 34% IF + 5% 3D458524 458523 1 91% 3/2[5/2] 66% 3D + 31% 'F + 3% 3F472520 472492 28 99% 1/2[5/2] -35% 'F - 36% 3F + 29% 3D

4 455444 455434 10 100% 3/2[7/2] 100% 3F

TABLE VIl. Calculated energy level values in cm-' and percentage compositions for the 4s4p6 4d + 4p 5 4f configurations of Zrv. States of 4s4p 6 4dare denoted by an asterisk. Negative eigenvector components are preceded by a minus sign.

J E (obs.) E (calc.) obs.-calc. % Jll Percentage composition-LS

1 434715 434629 86 64%3D* + 36%3D460477 460626 -149 64% 3/2[3/2] 64% 3D - 36% 3D*

2 435759 435813 -54 66% 3 D* + 33% 3D + 1% 3F450134 450134 0 -76% lD*-21% lD + 2% 3F-1% 3D460694 460566 128 55% 3/2[5/2] -41% 3D - 33% 3F + 25% 3 D* + 1% 'D464015 464016 -1 42% 3/2[3/2] 31% ID - 29% 3F - 19% lD* + 14% 3D - 7% 3D*476130 476131 -1 90% 1/2[5/2] 47% 'D + 35% 3F - 11% 3D - 5% 'D* + 2% 3D*

3 437678 437706 -28 -71% 3D* - 27% 3D-1% 3F-1% IF457 547 457 680 -133 95% 3/2[7/2] -46% 3G + 30% 'F - 24% 3F460768 460682 86 79% 3/2[5/2] -31% 3D - 27% 3F + 21% 3 D* - 21% IF470774 470898 -124 95% 1/2[7/2] -54% 3G - 26% IF + 19% 3F473715 473648 67 91% 1/2[5/2] 41% 3D - 29% 3F - 21% 'F - 8% 3D*

4 454539 454584 -45 95% 3/2[9/2] 61% 3G - 37% IG + 2% 3F458432 458449 -17 93% 3/2[7/2] 57% 3F + 33% IG + 10% 3G471762 471690 72 97% 1/2[7/2] 41% 3F - 30% 'G - 28% 3G

5 453681 453566 115 100% 3/2[9/21 100% 3G

250 J. Opt. Soc. Am., Vol. 69, No. 2, February 1979 Joseph Reader and Nicolo Acquista 250

TABLE VIII. Calculated energy level values in cm- and percentage compositions for the 4p5 5g configuration of Zrv. Negative eigenvector componentsare preceded by a minus sign.

J E (obs.) E (calc.) obs.-calc. % Jil Percentage composition-LS

2 536682 536674 8 100% 3/2[5/2] 100% 3F

3 536732 536731 1 100% 3/2[5/2] 61% 3F + 39% 'F537 539 537 535 4 99% 3/2[7/21 54% 3G - 30% 'F + 16% 3F552934 552939 -5 100% 1/2[7/2] 46% 3G + 31% 'F - 22% 3F

4 537 502 537 495 7 100% 3/2[7/2] -46% 3F - 30% 3G - 24% 'G537807 537811 -4 100% 3/2[9/2] 39% 'G - 31% 3G - 30% 3H552878 552880 -2 100% 1/2[9/2] 70% 3H + 17% 'G - 13% 3G552894 552896 -2 100% 1/2[7/2] 54% 3F - 26% 3G - 20% 'G

5 536984 536988 -4 100% 3/2[11/2] -54% 'H + 46% 3H537816 537815 1 100% 3/2[9/2] 70% 3G + 16% 3H + 14% 'H552895 552888 7 100% 1/2[9/2] -38% 3H - 32% 'H + 30% 3G

6 536961 536973 -12 100% 3/2[11/2] 100% 3H

4p5 5g and 6g configurationsThe 4p5 5g levels are plotted in Fig. 6. The results of the

least-squares calculations are given in Table VIII; the pa-rameter values are given in Table IV. Also given in Table IVare the parameter values for the 4p5 6g configuration. In4p56g the 1/2[7/213 level has not been found. It is possiblethat the transition usually used to establish this level,4p5 4f 1/2[5/2]2-4p5 6g 1/2[7/2]3, is blended with the CII lineat 903.962 A and has therefore not been detected. The cou-pling in both 4p 5 5g and 4p 5 6g is nearly pure J1l.

480

'E000

w

zW

460 -

4401-

1 2 3

J VALUE

4 5

FIG. 4. Structure of the 4p5 4fand 4s4p64dconfigurations of Zrv. Heavylines, 4p5 4f; dashed lines, 4s4p 6 4d. The levels of 4p5 4fare designatedin J Icoupling.


It is interesting to note that although the intervals betweensuccessive Jl pairs decrease substantially in going from 4pp5 5gto 4pp5 6g, the pair splittings themselves hardly decrease at all.This near constancy of the pair splittings is reflected in thefitted values of G3(pg) and G 5 (pg), which are practicallyconstant. This trend is indeed predicted by the HF calcula-tions. Similar effects in the 4p5 ng configurations of Rbii andSr III have been noticed earlier.14

We also note that the fitted values of t4p in the 4p 5 5g and4p 5 6g configurations are very close to the value t4p of 10402cm' found in the 4p5 2p core of ZrVI. In fact the ratio oft4p(4p 5 5g) to t4p( 4 p5 ) along the sequence is very regular:0.9997 for Rb, 0.9991 for Sr, 0.9987 for Y, and 0.9983 for Zr.The fitted/HF ratios for t4p (4p 5 5g) along the sequence are

E

0000

wzw

4601-

4401 2 3

J VALUE

4 5

FIG. 5. Positions of the 4p 5 4f and 4s4p 6 4d levels calculated withoutconfiguration interaction. Heavy lines, 4p5 4f; dashed lines, 4s4p64d.


I I I I I

I A -

T [2[ ]

4p5 4f

I p] 2 K2] [_/ . [2]

---- 'D

4s 4p64d

-I I 3D

--- I I

I T I T-

44% 1D

9 9% 3D%3D I

4 2 P954

4p 54f

32

I [i.] 31/3 1 D4s 4p 6 4d

--- 3D

I I I I Il l l l l

I

3 55 1 53% 1D

T r2 J

F'3 1-11

1 D ---- 71%3D

I I I I I

" Rl] --- 2

4p5 5g

32

I I2 3 4

J VALUE

[2] -

5 6

FIG. 6. Structure of the 4p 5 5g configuration of Zrv. The levels ardesignated in J, /coupling.

553 000

ACKNOWLEDGMENT

550 F

E

a:

000

CDw:zZ

540

5301

0 1 2J VALUE

3 4

FIG. 7. Structure of the 4p5 6d and 4p5 7s levels of Zrv. Heavy lines,4p5 6dt, dashed lines, 4p57s. The levels are designated in J./ coupling.Predicted positions of levels not observed experimentally are shown as thinlines.

1.1074 for RbII, 1.1051 for SrIH1, 1.1035 for YIV, and 1.1023for Zr V.

4p5(6d + 7s) configurationsThe 4p 5 (6d + 7s) levels are plotted in Fig. 7. As shown,

four levels of 4p5 6d have not been found. The parametervalues are given in Table IV.


This work was supported in part by the Division of Mag-netic Fusion Energy of the U.S. Department of Energy.

'M. S. Z. Chaghtai, "Vacuum Spark Spectra of Zirconium, Niobium,and Molybenum," Phys. Scr. 1, 31-35 (1970).

2 J. Reader, G. L. Epstein, and J. 0. Ekberg, "Spectra of Rb II, Sr IlI,YIV, Zrv, NbvI, and Mo VII in the Vacuum Ultraviolet," J. Opt.Soc. Am. 62, 273-284 (1972).

3C. B. Ross, "Wavelengths and Energy Levels of Singly IonizedCopper, Cu rI," Los Alamos Scientific Laboratory Report No. 4498(available from National Technical Information Service, Spring-field, Va. 22161).

4J. Reader, C. H. Corliss, and R. Zalubas, "Reference Wavelengthsof Y v in the 200-460 A Region," program and abstracts of AtomicSpectroscopy Symposium, National Bureau of Standards, Wash-ington, D.C., 1975.

5 G. L. Epstein and J. Reader, "Spectrum of doubly ionized yttrium(YIII)," J. Opt. Soc. Am. 65, 310-314 (1975).

6J. Reader and G. L. Epstein, "Analysis of the Spectrum of QuadruplyIonized Yttrium (Yv)," J. Opt. Soc. Am. 62, 619-622 (1972).

7 R. Zalubas, J. Reader and C. H. Corliss, "4s2 4 p 4 -4 s 4 p 5 transitionsin five-times ionized yttrium (YvI)," J. Opt. Soc. Am. 66, 35-36(1976).

8B. Edlen, "Wellenlingen und Termsysteme zu den Atomspektrender Elemente Lithium, Beryllium, Bor, Kohlenstoff, Stickstoff undSauerstoff," Nova Acta Regiae Soc. Sci. Ups. (IV) 9, No. 6(1934).

9B. Edl6n, "Wavelength Measurements in the Vacuum Ultraviolet,"Rep. Prog. Phys. 26,181-212 (1963).

10R. L. Kelly and L. J. Palumbo, Atomic and Ionic Emission LinesBelow 2000 Angstroms-Hydrogen Through Krypton, Naval Re-search Laboratory Report 7599 (U.S. GPO, Washington, D.C.1973).

"V. Kaufman and B. Edl6n, "Reference Wavelengths from AtomicSpectra in the Range 15 A to 25000 A," J. Phys. Chem. Ref. Data3, 825-895 (1974).

'2 C. Froese, "Numerical Solution of the Hartree-Fock Equations,"Can. J. Phys. 41, 1895-1910 (1963); and C. Froese-Fischer and M.Wilson, "Programs for Atomic Structure Calculations," ArgonneNational Laboratory Report No. 7404 (available from NationalTechnical Information Service, Springfield, Va. 22161).


552 6001-

Higher 4p 5 nd and ns configurationsThe levels of the 4p9 7d, 8s, 9s, 10s and 4s4p 6 5p configu-

rations listed in Table III are all J = 1 levels established byresonance lines from Ref. 2. In our present work we con-firmed the ionization stage of these lines. For the sake ofuniformity we have designated these 4p 5 nd and ns levels inJ1l coupling. For the 4p5 nd levels the J,1 designations aremore physically significant than the LS designations used inRef. 2.

IONIZATION ENERGY

In Ref. 2 a value of 648250 + 150 cm'1 was given for theionization energy of Zr v. This was based on the limit of theobserved 4p5 ns series. If we now use the center of gravity ofthe observed 4p 5(2P3/2)ng, n = 5,6 levels together with a valueof An* (6g-5g) = 0.9956 ± 0.0010, as implied by the corre-sponding values in Rb II (0.9989) and Sr III (0.9978), we derivea value for the limit of 648050 ± 60 cm-' (80.349 ± 0.007

re eV).

,E000

CDa:zw

537 8001-

537 4001-

537 0001-

536 600

I I I I

4P5 (6d +7s) -

I .1 I ,

7 [32] , [§.]

2~ [2J --

5 1E] a T T ]

. . . . .

I

3- 1 [21]

I I

1"J. Reader and G. L. Epstein, "Zeeman effect and revised analysisof singly ionized rubidium (Rb II)" J. Opt. Soc. Am. 63, 1153-1167(1973).

14

J. Reader, "Spectrum and energy levels of singly ionized rubidium(RbII)," J. Opt. Soc. Am. 65, 258-301 (1975).

5 J. E. Hansen and W. Persson, "Configuration Interaction in theSpectrum of Sr III," Phys. Scr. 8, 279-284 (1973).

16J. Reader and G. L. Epstein [unpublished analysis of the spectrumof Yiv (1978)].

'7Optimization of the level values was done with the computer pro-gram ELCALC due to L. J. Radziemski, Jr.

18J. E. Hansen, W. Persson, and A. Borgstr6m, "3s3p 63d-3s23p5 nfInteraction in Ca II and Identification of the 3s3p6 3d Configura-tion," Phys. Scr. 11, 31-37 (1975).

Radiative-lifetime measurements for I and I iiAkihiro Kono and Shuzo Hattori

Department of Electronic Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464, Japan(Received 30 August 1978; revised 28 October 1978)

Delayed-coincidence measurements of radiative lifetimes have been made on 3 levels in the5p ' 6p configuration of I i and 11 levels in the 5p 3 6p configuration of I ii. Some of the levels arepertinent to the neutral iodine laser transitions and the He-I+ laser transitions. For these measure-ments, a new excitation method has been developed in which a discharge plasma is utilized as anelectron source.

There has been little experimental work on the radiativelifetimes of the excited states of neutral and singly-ionizediodine. Most of the measurements have been made on theresonance transitions and the forbidden lines of I i.1-5 Ex-cited-state measurements are of interest because of their ab-sence in the literature and of their importance for under-standing the excitation mechanism of He-I+ lasers and neutraliodine lasers. In this paper we report on delayed-coincidencemeasurements of the radiative lifetimes for 3 levels in the5p 4 6p configuration of II and 11 levels in the 5p 3 6p config-uration of I II. Some of the levels are directly involved in laseraction.

EXPERIMENTAL TECHNIQUE

Photon decay curves following electron impact excitationare recorded with a 256-channel delayed-coincidence analyzerconsisting of a time-to-amplitude converter, a DA converter,and a microcomputer. The technique is in principle the sameas that described by Bennett et al.,

6 but a new excitation tubeis used in place of a hot-cathode excitation tube.

Diodes or triodes with hot oxide-coated cathodes are notsuitable for excitation of iodine since oxide-coated cathodeare deactivated by iodine. Use of a tungsten cathode wouldseriously reduce the signal-to-background ratio in the visibleand near infrared region, where our measurements are made.We have thus developed the excitation tube which utilizes adischarge plasma as an electron source. The excitation tubeis shown in Fig. 1. A continuous discharge is maintainedbetween the cathode and the anode-1. A pulsed voltage isapplied between the anode-1 and the anode-2, and electronsin the plasma are extracted through the meshed anode-1 toexcite a sample gas. The following optical decay in the gapbetween the anodes is observed.

The excitation pulse used was 100 ns long and 30 V in am-plitude. Average channel widths of the analyzer calibrated

with a crystal time base are 3.04 and 1.34 ns. The longerchannel width was mostly used for measurements for neutrallevels and the shorter channel width for ionic levels. Decaycurves observed after the excitation pulse is cut off are fittedto a sum of two exponential terms plus a background constantwith a computer program for nonlinear least-squares analysis.In all cases reported here, lifetimes are those given by therapidly-decaying exponentials.

HELIUM MEASUREMENTS

In order to test the excitation method, the lifetimes of theHe levels 31S, 31p, 41D, 33S, 33 P, and 33D were measuredusing the emission at 7281, 5016, 4922, 7065, 3889, and 5876A, respectively. Measurements were made at low heliumpressures to avoid the effect of resonance trapping, and neonwas added as a buffer gas to sustain discharge. The lifetimeof the 3 'P level obtained at the helium pressure of 1 mtorr andthe neon pressure of 300 mtorr was 5.3 + 0.5 ns, which givesthe upper limit of the system time resolution although theultimate value is not known. Measurements for other levelswere made at several neon pressures ranging from 200 to 570mtorr with the helium pressure fixed at 3 mtorr. Observeddecay rates showed dependence on the neon pressure. Inorder to obtain the radiative lifetimes, they were fitted to thefunction

R = A + nvQ,

where R is the observed decay rate, n the density of neonatoms, v the mean relative velocity between helium atoms andneon atoms, and A and Q are the adjustable parameters cor-responding respectively to the radiative decay rate and thede-excitation cross section for helium in neon. The resultsare summarized in Table I together with the lifetimes due toother workers. The good agreement between our lifetimesand those due to others shows that the present method givesreliable lifetimes.

253 J. Opt. Soc. Am., Vol. 69, No. 2, February 1979 0030-3941/79/020253-03$00.50 C 1979 Optical Society of America 253

Spectrum and energy levels of four-times ionized zirconium (Zr v)

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Transcript of Spectrum and energy levels of four-times ionized zirconium (Zr v)