1. Optical Stark Spectroscopy and Hyperfine study of Gold Sulfide (AuS)
Ruohan Zhang, Damian Kokkin and Timothy C. Steimle
International Symposium on Molecular Spectroscopy
70th Meeting (UIUC)
June 22-26, 2015

2. Strong relativistic effect
Motivation:
Gold chemistry
Strong relativistic effect
Previous spectroscopic studies on AuS(very few):
Photoelectron Spectroscopy(AuS-):
Prof. Lineberger’s group, J. Phys. Chem. A, 108, 11307(2004).
Prof. L.-S. Wang’s group, J. Am. Chem. Soc., 130, 9156(2008).
Prof. L.-S. Wang’s group, J. Phys. Chem. Lett., 6, 637(2015).
Theoretical work:
Z. J. Wu, J. Phys. Chem. A, 109, 5951(2005) DFT
P. Schwerdtheger, J. Phys. Chem, 91, 1762(1989) Rel-HF
E. Kraka et al, Croat. Chem. Acta, 82, 233(2009) DFT
dipole moment
Electronic Spectroscopy(our group):
Low-resolution: Dr. Kokkin’s talk(TA02)
High-resolution: rotational & hyperfine analysis, Stark & Zeeman effect

3. Introduction AuS molecular orbital(MO) diagram: Groud state:
(1s)2(1p)4(1d)4(2s)2(2p*)3  X2P
Excited states:
(1s)2(1p)4(1d)4(2s)1(2p*)4  A2S+
(1s)2(1p)4(1d)4(2s)2(2p*)2(3s*)1 a4S, B2S-, C2D, D2S
Low resolution observation(at ASU & Macalester(Prof. Varberg))
C2D5/2-X2P3/2
C2D3/2-X2P3/2
Excitation spectra of AuS

4. Experimental approaches
High-resolution spectrometer
Linewidth ~30MHz
Stark plates
Optical Stark Spectroscopy
PMT
Gated photon counter
Laser induced
fluorescence(LIF)
Ablation laser(532nm)
Pulse
valve
OCS in Argon
Well collimated
cold molecular beam, <15 K
skimmer
Au rod
CW-dye laser
Source
chamber
Detection
chamber
Diffusion pump II
Diffusion pump I
Background pressure (10-6 torr)

5. Observation – Field free

6. Observation: C2D3/2-X2P3/2 a b c d A B C D
Conclusion: Small ground state hyperfine interaction.(Same as 2D5/2)

7. Observation a b c d A B C D
Conclusion: 1. The hyperfine interaction are different between the two excited states.
2. No parity-dependent hyperfine interaction were observed.

8. Field Free Analysis: treat C2D5/2 and C2D3/2 separately
X2P3/2: No -dbl.; no hyperfine 
Heff= BJ2
C2D3/2 and C2D5/2 :No -dbl but hyperfine
Heff= Tv’v’’ +BJ2 + Hmhf (Au) + Hquad(Au)
The magnetic hyperfine Hamiltonian (not Λ-doubling dependent)
One Ω component
Frosch and Foley terms
h3/2(2D)=2a−(1/2)(bF+2c/3), h5/2(2D)=2a+(1/2)(bF+2c/3)

9. Field Free Analysis: treat C2D5/2 and C2D3/2 separately (cont.)
nuclear-electric quadrupole interactions - 2 parameters: eq0Q and eq2Q
Matrix representation
Diagonalization
Transition
wavenumbers
Energies
Fitting procedure:
C2D3/2 State
71 data
Parameters of C2D3/2
Observed transitions
78 data
Parameters of C2D5/2
C2D5/2 State

10. Results
Fitted parameters (Unit: cm-1)

11. AuS Stark measurement(in progress)
Electric dipole moment(mel)
Theoretical calculation:
For ground state(X2P): mel1=4.69; mel2=2.63
Challenges:
Complicate and congested hyperfine features;
Numerous splitting features caused by higher F values;
S/N get worse with increased electric field.
P. Schwerdtheger et al, J. Phys. Chem, 91, 1762(1989)
E. Kraka et al, Croat. Chem. Acta, 82, 233(2009)

12. Stark observation(in progress)
Lower J values, lower F values;
Lower electric field;
Repeat and co-add the scans.
C2D3/2/2
complicated
X2P3/2
F”=2
Q(3/2)
F”=1
MF=F, F-1, …, -F+1, -F
MJ=J, J-1, …, -J+1, -J

13. Conclusion and future work
The high-resolution spectra of the 2D3/2-X2P3/2 and 2D5/2-X2P3/2 transitions of AuS have been recorded by the first time.
The spectroscopic parameters included the hyperfine parameters of the two states have been determined.
The Stark effect was measured and will be analyzed to determine the electric dipole moment of AuS.
The Zeeman effect of AuS will be determined in the future.

14. Acknowledgements Arizona State University Macalester College
Timothy C. Steimle
Damian L. Kokkin
Trung Nguyen
Macalester College
Thomas D. Varberg

15. Thank you!