1. Optical Stark Spectroscopy and Hyperfine study of Gold Sulfide (AuS)
Ruohan Zhang and Timothy C. Steimle
International Symposium on Molecular Spectroscopy
71th Meeting (UIUC)
June 20-24, 2016

2. Gold-Sulfur Bonding Au-S bonding Au-S cites
Many reviews have appeared describing the study and use of the gold-thiol systems in molecular biology, inorganic chemistry, self-assembled monolayers and molecular electronics. Much of this work has been done to understand the interaction only on the nanoscale.

3. Previous 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. Schwerdtfeger et al, J. Phys. Chem, 91, 1762(1989) Rel-HF
E. Kraka et al, Croat. Chem. Acta, 82, 233(2009) DFT
dipole moment
Prof. Cheng, John Hopkins University
Ab initio calculation on dipole moment
Electronic Spectroscopy(our group):
Low-resolution & High-resolution

4. Previous work(our group):
Low-resolution study on AuS:
D. Kokkin; R. Zhang; T. Stemle; I. Wyse; B. Pearlman; T. Varberg, J. Phys. Chem. A, 2015, 119 (48)
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
Macalester
(Prof. Varberg))
ASU A B C D

5. Optical Stark Spectroscopy
Experimental Setup
High-resolution spectrometer
Linewidth ~30MHz
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
Stark plates
Au rod
CW-dye laser
Source
chamber
Detection
chamber
Diffusion pump II
Diffusion pump I
Background pressure (10-6 torr)

6. High-resolution Spectra
B2SX2P3/2
R1(2.5)
SR21(2.5)

7. Hyperfine Structure A B C D B D + C A a b c d - d c b a
+/-

8. The effective Hamiltonian:
Field Free Analysis:
The effective Hamiltonian:
X2P3/2 :
Heff= BJ2+ Hmhf (Au) + Hquad(Au)
B2S-:
Heff= Tv’v’’ +BN2 +(g+gDN2)N·S+Hmhf (Au) + Hquad(Au)
The magnetic hyperfine Hamiltonian (not Λ-doubling dependent)
Hmhf= aI·L+bI·S+cIzSz
One Ω component
Frosch and Foley terms
Hmhf= [aLz+(b+c) Sz]Iz= [aLz+(bF+ 𝟐 𝟑 c) Sz]Iz =hWIz
h3/2(2P)=a+(1/2)(bF+c),
The nuclear-electric quadrupole interactions:
Matrix representation
Diagonalization
Transition
wavenumbers
Energies
Fitting procedure:
~200 data
Fitted Parameters
Observed transitions

9. Results X2P3/2 B” 0.13155(1) D”(×107) 0.64(1) h3/2” -0.00261(5) eq0Q”
Fitted field-free parameters( in cm-1)
X2P3/2 B”
(1)
D”(×107)
0.64(1)
h3/2”
(5)
eq0Q”
0.0027(1) Au S
B2S B’
(1)
D’ (×107)
0.54(1)
g ’
(6)
gD ’(×105)
-1.18(6)
bF’
(4) c’
0.027(1)
eq0Q’
0.0062(4)
T00’
(2)
Large spin-rotation interaction(mixing of states)
Large hyperfine interaction in the excited states
RMS = cm-1

10. AuS Stark measurement Electric dipole moment(mel) Challenges:
0.2 cm-1
Electric dipole moment(mel)
Previous theoretical calculation:
For ground state(X2P): mel1=4.69 D; mel2=2.63 D
Prediction from Prof. Cheng’s work: mel=2.44 D
Q1(5.5)
Q1(4.5)
RQ21(12.5)
QP21(2.5)
Challenges:
RQ21(12.5)
F”=4→F’=3
Complicate and congested hyperfine features;
Numerous splitting features caused by higher F values
P. Schwerdtfeger et al, J. Phys. Chem, 91, 1762(1989)
E. Kraka et al, Croat. Chem. Acta, 82, 233(2009)

11. Stark measurements F’ MF’ a b c d e f A B C D 3 b c d a e f MJ” F”+3 To -3 3 b c d a e f
MJ” F”
-5/2
-3/2 B C D 1 A
-1/2 2 3
+1/2 4
F”=4→F’=3
+3/2
+5/2

12. Results Stark shift Dipole moments 45 data RMS = 13 MHz X2P3/2
Experimental
Theoretical
ASU
2.161 ± 0.055
Massey1
4.69
Southern Methodist2
2.63
(unit: Debye)
JHU
2.44
mel/re
Gold-containing molecules
mel (Debye)
re(A)
mel /re(D/A)
AuO
2.93(8)
1.853
1.58
AuF
4.13(2)
1.924
2.15
AuS
2.16(5)
1.00
AuCl
3.69(2)
2.205
1.67
AuF 4
AuO 3
AuCl 2
AuS 1
P. Schwerdtfeger et al, J. Phys. Chem, 91, 1762(1989);
E. Kraka et al, Croat. Chem. Acta, 82, 233(2009);
T. Okabayashi et al, Chem. Phys. Let. 43, 223(2005);
M. Gerry et al, J. Am. Chem. Soc., 122, 1560(2000),
M. Gerry et al, J. Mol. Spectroc. 203, 105(2000).
1.0
2.0
3.0
4.0
Electronegativity

13. Conclusion and Future work
The high-resolution spectra of the B2S--X2P3/2 transitions of AuS have been recorded by the first time;
The spectroscopic parameters included the hyperfine parameters of this stated have been determined;
The electric dipole moment of AuS has been determined;
The Zeeman effect of AuS will be determined in the future.

14. Acknowledgements Arizona State University John Hopkins University
Timothy C. Steimle
Trung Nguyen
John Hopkins University
Lan Cheng

15. Thank you!