June 26, 200964th International Symposium on Molecular Spectroscopy

The Pure Rotational Spectrum of ZnS (X1+)

Lindsay N. Zack

Lucy M. ZiurysDepartment of Chemistry, Department of Astronomy, Steward

Observatory, and Arizona Radio Observatory

University of Arizona

June 26, 200964th International Symposium on Molecular Spectroscopy

Previous Work• Mass spectrometry

– Dissociation energy (Marquart and Berkowitz 1963; de Maria et al. 1965)

• Spectroscopic measurements– Absorption spectroscopy of ZnS in 7000-1900 region (Sen-Gupta

1933)

– X-ray emission and luminescence spectroscopy of crystals and nanoparticles (Laihia et al. 1996; Denzler et al. 1998)

• Theoretical calculations– Different levels of theory with and without relativistic

corrections (e.g. Bauschlicher and Langhoff 1986; Peterson et al. 2007)

– Similarities between single molecule and bulk properties (Anderson et al. 1987; Bridgeman and Rothery 2000; Chambaud et al. 2008)

– re ~ 2.04 – 2.12 Å

June 26, 200964th International Symposium on Molecular Spectroscopy

Instrumentation

• Direct-absorption spectroscopy

• Phase-locked Gunn oscillators and Schottky diode multipliers (65-850 GHz)

• Gaussian beam optics

• Reaction chamber: double-pass, water-cooled steel cell containing a Broida-type oven

• InSb bolometer detector

• Radiation is modulated at 25 kHz and detected at 2f

June 26, 200964th International Symposium on Molecular Spectroscopy

Direct-absorption mm/sub-mm wave

spectrometer

June 26, 200964th International Symposium on Molecular Spectroscopy

Molecular Synthesis• Gas-phase synthesis

• Zinc vapor produced in Broida-type oven– Alumina crucible in tungsten wire basket

– m.p. 420 C

• H2S added over top of oven

• Argon carrier gas

• d.c. discharge needed (250 mA at 200 V)

June 26, 200964th International Symposium on Molecular Spectroscopy

42 GHz (~7B) initially scanned continuosly

Frequency (MHz)

380000 390000 400000 410000

June 26, 200964th International Symposium on Molecular Spectroscopy

Frequency (MHz)

376000 378000 380000 382000 384000

64Zn : 66Zn : 67ZnS: 68Zn : 70Zn 49: 28: 4: 19: 0.6%

64ZnSv = 0

68ZnSv = 0

66ZnSv = 1

67ZnSv = 0

66ZnSv = 0

64ZnSv = 1

June 26, 200964th International Symposium on Molecular Spectroscopy

Frequency (MHz)

414581 414606 417000 417025

64 ZnS (X 1+): J = 37 36

v = 1

v = 0

June 26, 200964th International Symposium on Molecular Spectroscopy

64ZnS 66ZnS 67ZnS 68ZnS

J’ J” v obs-calc obs-calc obs-calc obs-calc

33 32 0 372 072.494 -0.028

34 33 0 383 312.402 0.010 379 453.171 -0.032 377 605.094 -0.013 375 817.323 -0.020

35 34 0 394 549.133 0.011 390 577.179 0.007 388 675.054 -0.016 386 835.077 0.003

36 35 0 405 782.628 0.008 401 698.004 0.029 399 741.917 0.021 397 849.714 0.016

37 36 0 417 012.800 0.006 412 815.526 0.006 410 805.501 0.005 408 861.131 0.003

38 37 0 428 239.552 <0.000 423 929.716 -0.001 421 865.783 0.002 419 869.277 0.002

40 39 0 450 682.455 0.005 446 147.698 -0.008 443 976.060 0.016 441 875.363 0.002

41 40 0 461 898.392 -0.130 457 251.325 0.008 455 025.849 0.005 452 873.127 0.003

42 41 0 468 351.209 -0.009 466 071.949 -0.020 463 867.240 -0.009

34 33 1 381 096.161 -0.015 377 270.558 0.016

35 34 1 392 267.552 0.022 388 330.111 -0.020

36 35 1 403 435.640 0.005

37 36 1 414 600.387 -0.013 410 439.672 0.001

38 37 1 425 761.723 -0.007 421 489.437 -0.002

40 39 1 448 073.724 0.007 443 578.528 0.011

41 40 1 459 224.195 0.007 454 617.644 -0.002

42 41 1 470 370.846 -0.008 465 653.042 -0.003

Transition Frequencies

June 26, 200964th International Symposium on Molecular Spectroscopy

Constants64ZnS 66ZnS 67ZnS 68ZnS

B0 5 645.8417(51) 5 588.9106150) 5 561.6491(50) 5 535.2749(50)

D0 0.0038472 (18) 0.0037701(17) 0.0037339(17) 0.0036978(17)

rms 0.013 0.016 0.014 0.010

Be 5 662.1143(81) 5 604.9376(80)

e 32.5452(71) 32.0540(73)

De 0.0038372(29) 0.0037606(27)

e -0.0000200(25) -0.0000190(24)

re (Å) 2.0464 2.0464

e (cm-1) 459 457

exe (cm-1) 2.09 2.07

DE,v=0 (eV) 3.12 3.12

Rotational and equilibrium constants for ZnS (1+)a.

a) In MHz unless otherwise indicated.

• Data fit using SPFIT (Pickett 1991)

• 7-8 transitions measured for 4 isotopologues• Hyperfine structure from 67Zn (I = 5/2) not observed• v = 0 and v = 1 for 64ZnS and 66ZnS• re = 2.0464 Å (theory: re ~ 2.04-2.12 Å)

June 26, 200964th International Symposium on Molecular Spectroscopy

3d Sulfide and Oxide Bond Lengths

“double-hump” structure

r0: TiO, VO, CrO, MnO, FeO, CuO, ScS, VS, MnS, FeS, CoSre: ScO, CoO, NiO, ZnO, TiS, CrS, NiS, CuS, ZnS

CuO-ZnO decrease: ~0.02 ÅCuS-ZnS decrease: ~0.003 Å

Less stabilization gained from addition of electron to the valence orbital in ZnS

June 26, 200964th International Symposium on Molecular Spectroscopy

Dissociation Energy

• Value estimated in this work higher than all previous studies

• Is Morse potential good assumption?

DE (ZnS) = 3.12 eV

DE (ZnO) = 3.41 eV

DE (ZnF) = 3.12 eV

DE (ZnCl) = 2.73 eV

Present StudyPeterson 2007de Maria 1965Boldyrev 1997

June 26, 200964th International Symposium on Molecular Spectroscopy

Summary

• Rotational spectra of four isotopologues of ZnS have been measured

• Rotational and equilibrium constants have been determined

• This work agrees well with theory with regards to bond lengths

• Dissociation energy is significantly higher than previous theoretical and experimental (mass spec) studies indicate

• Similarities in bonding trends between oxides and sulfides

June 26, 200964th International Symposium on Molecular Spectroscopy

Acknowledgements• Professor Lucy Ziurys

• Dr. DeWayne Halfen

• Robin Pulliam, Brent Harris, Ming Sun, Emmy Tenenbaum, Jessica Dodd, Gilles Adande, Matthew Bucchino, and Jie Min

• Funding- NSF and NASA