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

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.

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

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

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)

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

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

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

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” 0.13155(1) D”(×107) 0.64(1) h3/2” -0.00261(5) eq0Q” 0.0027(1) Au S B2S B’ 0.12347(1) D’ (×107) 0.54(1) g ’ 0.13640(6) gD ’(×105) -1.18(6) bF’ -0.0216(4) c’ 0.027(1) eq0Q’ 0.0062(4) T00’ 15638.0666(2) Large spin-rotation interaction(mixing of states) Large hyperfine interaction in the excited states RMS = 0.0009 cm-1

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)

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

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

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.

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

Thank you!