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The Rotational Spectrum and Hyperfine Constants of Arsenic Monophosphide, AsP
Flora Leung, Stephen A. Cooke and Michael C. L. Gerry
Department of Chemistry, The University of British Columbia,
2036 Main Mall, Vancouver, B. C. Canada, V6T 1Z1
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Introduction• All intergroup 15 diatomics have been
spectroscopically studied. Hyperfine structure for PN(a), SbN, SbP(b), BiN, BiP(c) has been observed.
AsP• 1969: 12 red-degraded bands were
observed. Suggested to be the 1 - X1 system.(d)
• 1970: Rotational analysis of the observed bands.(e)
a Raymonda & Klemperer, J. Chem. Phys. 1971, 55, 232b Cooke & Gerry, PCCP, 2004, 6, 4579c Cooke, Michaud & Gerry, J. Mol. Struct. 2004, 695, 13
d Yee & Jones, Chem. Comm. 1969, 586e Harding, Jones & Yee, Can. J. Phys. 1970, 48, 2842
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Prediction of AsP Transition Frequencies.
• Based on rotational constant of Harding, Yee and Jones, Be = 5771 MHz.
• DFT QZ4P/SAOP calculations provided an estimate for eQq(75As) = -247.7 MHz
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AsP
Portion of spectrashown required 1000 avg. cyclesand is displayed asa 4k transformation.
Transitions shown are from J = 1 - 0 rotationaltransition. The groupon the left is from withinthe v = 0 state, that on the right from within the v = 1 state.
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Data Set• AsP has only one isotopomer.
• Hyperfine structure from As (nuclear spin, I = 3/2).
• Magnetic hyperfine structure from P (nuclear spin, I = 1/2).
• J = 1 - 0 and 2 - 1 transitions were observed in the vibrational ground state and first excited vibrational state.
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Equilibrium Spectroscopic Parameters for AsP
Parameter AsP
Be / MHz 5768.07932(92)
e / MHz 23.96044(90)De / kHz 2.17(13)
eQq(75As) / MHz -249.0963(75)CI(75As) / kHz 25.6(7)CI(31P) / kHz 23.6(2)
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Equilibrium Bond Lengths of Group V Phosphides
Molecule Bond Length / Å
PN 1.4909a
P2 1.8934b
AsP 1.9995SbP 2.2054c
BiP 2.2962d
AsP equilibrium bond length:e
e BCr 2
2
17
2 810
AhNC
re(AsP) = 1.99954398(16) Å
a Ahmed & Hamilton, JMS, 1995, 169, p.286b Rao & Laksham, IJPAP, 1970, 8, p.617
C Cooke & Gerry, PCCP, 2004, 6, p.4579d Cooke, Michaud & Gerry, J. Mol. Struct, 2004, 695-696, p.13
r(P-H) in PH3 = 1.42Å
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“Triple-bond covalent radii”
0.54 Å
0.94 Å
1.06 Å
1.27 Å
1.35 Å
Pekka Pyykkö, Sebastian Riedel and Michael Patzschke
Chemistry: A European Journal, 2005, 11, p.3511
“A coherent bond length amplified by some 24 character in the wave function will form an entrance ticket to the data set”
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Empirical Relationships for AsP:2
2 16
e
eeeee B
Bx
Parameter This Work Previous Expt’sa
e / cm-1 627(18) 604.02
exe / cm-1 2.04(8) 1.98
a Harding, Jones & Yee, Can. J. Phys. 1970, 48, 2842
e
ee D
B34
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Force Constants and Dissociation Energies for the Group 15 Phosphides
2)2( ek ee
ediss x
E
4
2
.
For AsP:
k = 507 Nm-1 and Ediss. = 576(40) kJ mol-1
lit. val. D00 = 430 kJ mol-1 (a)
a Gingerich, Cocke & Kordis, J. Phys. Chem. 1974, 78, 603
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Force Constants and Dissociation Energies for the Group 15 Phosphides
200300400500600700
200 400 600 800
Diss. Energy (kJ/Mol)
Forc
e. C
onst
. (N
/m)
HRMS
Mass Spec.(a)
BiP
SbP
AsP
P2
PNPN
P2
AsP
SbP
BiP
For the Morse potential k = 22Ediss.
a Gingerich, Cocke & Kordis, J. Phys. Chem. 1974, 78, 603
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Hyperfine Constants
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eQqe(75As) value in AsP = -249.0963(75) MHz(DFT value = -247.7 MHz)
eQq(X) / MHz q(X) / 1022 V m-2
PN (X=N) -5.1416(5) -1.040(2)
AsP (X=As) -249.0963(75) -3.28(6)121SbP (X=Sb) 617.4417(41) -3.82(9)a to -7.1(9)b
BiP (X=Bi) 898.2172(46) -7.20(22)
a Using most recent literature value for Q, (= -66.9(15) fm2): Svane, Phys. Rev. B, 2003, 68, 64422.b Using Q (= -36(4) fm2) value tabulated by Pyykko, Mol. Phys. 2001, 99, 1617.
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-8
-6
-4
-2
0
Fiel
d G
radi
ent (
10^2
2 V
/ m)
PN AsP SbP BiP
Field Gradients at the non-phosphorus nucleus in thegroup V phosphides.
(PP)
Using DFT we calculated q at Sb in SbP to be - 4.7 1022 V m-1.
Our results suggests a better value for Q(121Sb) of ~ 50 fm2.
Using Q(121Sb) = -66 fm2
Using Q(121Sb) = -36 fm2
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Vibrational Dependence of eQq
• For all of the group V phosphides for which appropriate data is available:
• Electronic ground states have asymptotes corresponding to atomic ground states of 4S3/2 for both atoms (i.e. an s2 p3 configuration)a.
• Increase in v → step toward this asymptote, at which point q at each atom is zero.
|eQq| ↓ as v ↑
a Alekseyev, Liebermann, Hirsch & Buenker, Chem. Phys. 1997, 225, p247
eQqv=0(75As) = -247.9495(46) eQqv=1(75As) = -245.6560(61)
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31P Nuclear Spin-Rotation Constants
Molecule CI (P) / kHz 106 CI (P)/ Be
PNa,b 78.2(5) 3.31AsP 23.6(2) 4.09SbPc 21(3) 4.98BiPd 23.7(6) 6.67
a Ahmed & Hamilton, JMS, 1995, 169, p.286b Raymonda & Klemperer, JCP, 1971,55, p.232
C Cooke & Gerry, PCCP, 2004, 6, p.4579d Cooke, Michaud & Gerry, J. Mol. Struct, 2004, 695-696, p.13
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05000
100001500020000250003000035000
3 4 5 6 7
Ab initio ValueToscano et al. ZPD, 1992, 22, p683
31P Nuclear Spin-Rotation Constants
106 CI (P) / Be
3 + -
1 + E
nerg
y Se
para
tion
/ cm
-1
PN
AsPSbP
BiP
01
1WWB
C
e
I
Where W1 - W0 is the energy gap between the ground
and first excited electronic states, a3+ - X1+.
Expt’l values: Rasanen et al. JCP, 1986, 85, p86Briedohr et al. JMS, 1995, 172, p369
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CInuc depends only on the nuclear positions.
CIelec depends on the ground and excited state wave functions.
Similarly: av = p + d
d depends on the ground state wave function.p is directly proportional to CI
el.
The relationship between CI and shielding constants
Flygare & Goodison:
elecI
nucII CCC
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As and P Nuclear Spin-Rotation Coupling Constants
More directly CI may be related to the span of the shielding tensor:
IeNe
p CBgm
m
2
75As 31P
CI / kHz 25.6(7) 23.6(2)p / ppm -2895(74) -1262(8)d / ppm 2920 1112av / ppm 25 -150 / ppm 4070(110) 3756(29)
calc. / ppm 5061 2391CI calc. / kHz 30.4 33.9
||
DFT calc.
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Conclusions• The pure rotational spectrum of AsP has been recorded for
the first time.
• eQq(75As) has been determined in AsP and compared with other known eQq values in related molecules. The comparison suggests an anomaly in Q(Sb).
• Nuclear spin-rotation coupling constants have provided useful electronic structure information for the series of Group 15 phosphides.
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Acknowledgements
UBC Mech. And Elec. WorkshopsThe Natural Sciences and Engineering Research Council of Canada (NSERC)