HYPERFINE SPLITTING AND ROTATIONAL ANALYSIS OF THE DIATOMIC MOLECULE ZINC

MONOSULFIDE, ZnS

DANIEL J. FROHMAN, G. S. GRUBBS II AND STEWART E. NOVICK

O.S.U. 2011

TC11

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Motivation & Goals

• Laser ablation allows FTMW study of refractory materials in the gas phase that were previously inaccessible to us: low vapor pressure materials, metals

• Halogens, nitrides, and sulfides of transition metals such as Cu and Zn in a vdW complex with H2 represent basic units within a metal organic framework (MOF) (NSF CHE – 1011214)

• MOF’s are a promising way to store and transport H2 safely and relatively inexpensively through physisorption

• ZnS microwave data necessary to prepare for our future projects involving diatomic zinc molecules complexed with hydrogen such as ZnS-H2 and ZnO-H2.

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1064 nm Nd:YAG Laser

• 4-5 ns pulse width, up to 20 Hz repetition1

•max power ~ 45 mJ/pulse1

•Interfaced with spectrometer’s controlling program, FTMW++2

•flashlamp is externally triggered by a N.I. CA-1000 pulse delay generator to give one laser pulse per nozzle pulse

1.) 90-1042A Polaris ST Operator’s Manual, New Wave Research, Inc., 20022.) Grabow, J.-U.; Ohio State University International Conference on Molecular Spectroscopy. Columbus, 2001.

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Ablation Nozzle

• Mounted on stationary mirror & modeled on Walker-Gerry design1

• 0.5 mm diameter General Valve Series 9 with ablation adapter head• Off-center 5.5 mm diameter bored out hole in adapter head 5 mm from nozzle exit contains ~ 5

mm ablation rod• Adapter head gas channel is 4.8 mm diameter and 22.6 mm in length• Laser enters through channel perpendicular to ablation rod and gas flow channels• Oriel motor mike and controller gives continuous vertical movement and rotation of rod with IR

triggers setting the travel distance

Walker, K. ; Gerry, M. J. Mol. Spec., 182 1997 178.

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Ablated Zinc

66

Ablated Zn Clip

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ZnS• Pure rotational spectrum of ZnS (1Σ+) with the first vibrational satellites (v=1) observed in mm-

wave1 which gives centrifugal distortion constants and rotational constants to predict spectra

• Microwave region studies can refine rotational constants with additional vibrational satellites (v = 1 to 5) and lower J transitions and observe 67Zn32S electric quadrupole splitting

• To our knowledge, no closed shell zinc diatomic species electric quadrupole hyperfine structure has been reported

• ZnS helps prepare for our future Zn containing vdW complex projects as well as a test of our ability to see transition metal species

Photo from http://www.webelements.com/zinc/1.) Zack, L.; Ziurys, L.; J. Mol. Spec. 257 2009 213

88

ZnS Production

99

Dunham Band Parameters

lk,

llk

klJv, 1)(JJ2

1vYE2l)/2(k

klkl μUY

2l)/2(kBkl

B

eAkl

A

eklkl μΔ

M

mΔ

M

m1UY

Watson, J.; J. Mol. Spec. 80 1980 411

2

1vβDD

2

1vε

2

1vδ

2

1vγ

2

1vαBB

eev

4

e

3

e

2

eeev

•Dunham band parameters, Ykl, are an approximation of isotopically mass dependent rotational and vibrational constants for diatomic molecules•Y01 ~Be, Y11~-αe, Y21~γe, Y31 ~ δe, Y41 ~ εe, Y12~ -βe, Y02~ -De, are used in a power series to describe vibration-rotation energies

•Under high resolution spectroscopy, Born-Oppenheimer approximation within Ykl may not hold•Significant deviation from the B.O. approximation may require modification of the band parameters to include B.O. breakdown (BOB) terms, Δkl

•BOB terms have an inversely proportional relation to atomic mass and thus may be be larger with lighter atoms

jje

iie μBμB

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Dunham Analysis

1.) Zack, L.; Ziurys, L.; J. Mol. Spec. 257 2009 2132.) Pickett, H.M., J. Molec. Spect. 148 1991 371

•All vibrational states of all isotopomers fit to one set of constants (Dunham band parameters) with reduced mass ratio scaling

•Δ01(Zn) was fit2 but found to be zero within experimental accuracy

•No Born-Oppenheimer breakdown was observed detected in the ground electronic state of ZnS up to v = 5

U01 120675.415 (36) MHz amu

U11 -3184.77 (40) MHz amu3/2

U21 -48.4 (13) MHz amu2

U31 29.5 (15) MHz amu5/2

U41 -29.92 (56) MHz amu3

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Spectroscopic constants for ZnSa (in MHz)

a. With the values of De and βe held to the values given in Ref 1 for 64Zn32S, 3.8372 kHz and -0.02 kHz respectively, and scaled appropriately for the other isotopomers.

1.) Zack, L.; Ziurys, L.; J. Mol. Spec. 257 2009 213

2.) Pickett, H.M., J. Molec. Spect. 148 1991 371

64Zn32S

(45.8%)

64Zn32S Ref 1 66Zn32S

(26.6%)

66Zn32S Ref 1 68Zn32S

(18.1%)

68Zn32S Ref 1

Be 5662.0442 (17) 5662.1143 (81)

5604.8677 (17) 5604.9476 (80)

5551.0029 (16) N/A

αe 32.3675 (41) 32.5452 (71) 31.8785 (41) 32.0540 (73) 31.4200 (40) N/A

γe -0.1066 (28) N/A -0.1044 (27) N/A -0.1024 (27) N/A

δe 0.01407 (70) N/A 0.01372 (69) N/A 0.01339 (67) N/A

εe -0.002471 (59) N/A -0.002397 (57) N/A -0.002329 (55) N/A

B0 5645.83577 (19)

5645.8417 (51)

5588.90427 (19)

5588.9106 (50)

5535.26894 (19)

5535.2749 (50)

B1 5613.28768 (19)

N/A 5556.84849 (19)

N/A 5503.67497 (19)

N/A

B2 5580.58500 (19)

N/A 5524.64155 (19)

N/A 5471.93315 (19)

N/A

B3 5547.68381 (19)

N/A 5492.24113 (19)

N/A 5440.00144 (19)

N/A

B4 5514.50311 (19)

N/A 5459.56855 (19)

N/A 5407.80525 (19)

N/A

B5 5480.87871 (19)

N/A 5426.46691 (19)

N/A 5375.19282 (19)

N/A

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67Zn32SThis work Ref. 1

B0 5561.64087 (50) 5561.6491 (50)

D0 0.0037339 (fixed) 0.0037339 (17)

9.331 (17) N/A

•Natural abundance of 67Zn32S is 3.9%

•I (67Zn) = 5/2

• eqQ = 13.620(8) MHz for 67Zn metal2

1.) Zack, L.; Ziurys, L.; J. Mol. Spec. 257 2009 213

2.) Kaufmann, E. N.; Brookeman, J.R.; Canepa, P.C.; Scott, T. A.; Rasmussen, D. H.; Perepezko, J. H. Solid State Commun. 29 1979 375

aa

1313

Conclusion• Our first laser ablation experiment was successful (ZnS)• Metal containing species are now accessible to us• 64Zn32S, 66Zn32S, & 68Zn32S observed up to v=5, 67Zn32S hyperfine splitting reported

• ZnS’s rotational structure has been refined and permits better prediction for ZnS-H2

• First reported closed shell 67Zn hyperfine structure• 64Zn34S isotopomer (0.6%) expected to be observed but for unknown reasons was absent• Dunham expansion analysis via Pickett software1 provides insight to other Zn containing

species and a method for similar analysis of other diatomics• Submitted to the Journal of Molecular Spectroscopy

1.) Pickett, H.M., J. Molec. Spect. 148 1991 371

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Acknowledgements

• Novick/Pringle group members for insight and help on this project

• Professor Pickett

• Wesleyan machine shop for helping on setting up our laser ablation capability

• NSF CHE – 1011214

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Laser Entry