Optical Stark Spectroscopy and Hyperfine study of Gold Chrolride (AuCl) Ruohan Zhang and Timothy C. Steimle International Symposium on Molecular Spectroscopy 69 th Meeting (UIUC) June16-20, 2014

Outline Motivation Introduction and previous work on AuCl Experimental setup and observation Hyperfine structure study of AuCl Stark measurements and determination of dipole moment(  el ) Gold chemistry Relativistic Effects (RE)

L. C. O’Brien et al, JMS. 194, 124 (1999). Fourier Transform Emission; microwave discharge H. Stoll group, Chem. Phys. 280, 71(2002) ab initio H. Stoll group, Phys. Rev. A, 76, (2007) ab initio K. Hirao et al, Int. J. Quant. Chem., 75, 757(1999) ab initio F. Neese et al, JCTC, 4, 908(2008 ) ab initio K. A. Peterson et al, Chem. Phys. 311, 177(2005) ab initio W. F. C. Ferguson, Physical Review, 21, 969(1928) Low-resolution Emission; Vapor Prof. Gerry’s group JMS. 203, 105(2000) FTMW, X 1  + state; supersonic expansion/Ablation Previous spectroscopic studies on AuCl Electronic Spectroscopy Theoretical work (very numerous;  15) : Prof. Tannimoto’s group JMS. 220, 155(2003) Millimeter & Sub-millimeter, X 1  + state; Hallow cathode discharge Microwave Spectroscopy X 1  + -A(  =1) and X 1  + - B(  =0 + ) are components of a X 1   transition dipole moment

 Electronic states of AuCl AuCl electronic configurations: AuCl molecular orbital(MO) diagram: 1 M. Guichemerrea, G. Chambauda, H. Stoll, Chem. Phys. 280, 71(2002) State energies 1 EOM-CC EOM-CC +S.O.

 Comparison of AuCl & AuF prediction (Stoll’s) AuCl AuF Can the  =0 + and 1 states be modelled as components of a strongly perturbed 3  state, hence validating the ab initio prediction? But from Prof. Varberg’s publication: “It has been shown that magnitude of the 197 AuF magnetic hyperfine is consistent with.. 3  1 … ”. i.e. the  =0 + and 1 state have little 3  characters.

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

Observation Low-resolution spectra High-resolution spectra Q(6)

A(  =1)-X: hyperfine splittings Narrower Wider

A(  =1)-X: hyperfine splittings Different Q-branch features in the same scale Energy level

Explanation of hyperfine splitting (large in e-parity levels ; small in f-parity levels) nuclear-electric quadrupole interactions - 2 parameters: eq 0 Q and eq 2 Q Three parameters are important for 3  1 state: Magnetic hyperfine interaction -a parameter: Frosch and Foley “a” H hyf = a I z L z Only eq 2 Q is parity dependent !

The Quadruple hyperfine parameters: Lower parity (R and P branches) Upper parity(Q branches) eQq 0 eQq 2 eQq 0 and eQq 2 eQq 0 eQq 0 and eQq 2

 Results Magnetic hyperfine Quadruple hyperfine 2-steps fitting process(Modeled as a 3  state) Fitted hyperfine parameters Fine structure parameters Step 2: hyperfine splitting Ground state parameter (From MW) Hyperfine structure parameters 78 data(  =1&  =0) Fixed Step 1: RMS= cm data RMS= cm -1 (O’Brain’s) 33

AuCl Q(1) AuF Q(1) ~1.2 GHz ~0.6GHz  Results The field-free transitions of A(  =1)-X and B(  =0)-X can be fitted together as the components of a X 1   transition. Comparison of AuCl & AuF in hyperfine structure Indicates that the (  =1) states of AuF and AuCl might be different.

X1X1 J=1 M J =0 MJ=1MJ=1 J=0 MJ=0MJ=0 C B A  Stark measurements Only the X 1  + - B 3   band transition was studied Electric Field Energy

 Anlysis 1.E. Goll, and H. Stoll, Phys. Rev. A, 76, (2007) 2.T. Suzumura, T. Nakajima, and K. Hirao, Int. J. Quant. Chem., 75, 757(1999) Stark shift Dipole moments 22 data RMS = 13 MHz X1+X1+ EXP3.69(2) DFT/LDA2.861NR-BOP5.922 DFT/B3LYP3.381ECP(HW)-BOP3.402 CAM-B3LYP3.861ECP(CER)-BOP3.532 CBS-CCSD(T)3.901RESC-BOP 030 EXP0.31(17)

Cu-XAg-XAu-X M-F5.26 [1] 6.22 [2] 4.13 [3] M-Cl???6.07 [4] 3.69 Excited state AuCl 3  AuF  Discussion Electric dipole moments,  el Ground state 3  ? Present study. B(  =0 + )  el = 2.68D  el = 0.33D [ 17.8 ](  =0 + ) Our previous study. [3] Different 1.F. Wang, and T. Steimle, J. Chem. Phys., 132, (2010) 2.K. P. R. Nair, and J. Hoeft, J. Phys. B, 17, 735(1984) 3.T. Steimle, R. Zhang and T. Varberg, J. Phys. Chem. A, 117, 17737(2013) 4.J. Hoeft, F. J. Lovas, E. Tiemann, and T. Törring, Z. Naturforsch. A 25, 35(1970)

Conclusion  The high-resolution spectra of the X 1  + -A(  =1) and X 1  + - B(  =0 + ) transitions have been recorded by the first time.  The A(  =1) and B(  =0 + ) states can be treated as components of a 3  state, and its spectroscopic parameters included the hyperfine parameters have been determined.  The electric dipole moment of AuCl have been determined.  The observed excited state of AuF are different from AuCl. Another relativistic ab initio prediction (Prof. Stanton/Dr. Lan Cheng) is needed.

Arizona State University Timothy Steimle Damian Kokkin (TK 12) Acknowledgements

Thank you!