The 66 th International Symposium on Molecular Spectroscopy, June 2010 Fang Wang,Anh Lee and Timothy C. Steimle Dept. Chem. & BioChem., Arizona State University, Tempe, AZ,USA Funded by: NSF Spectroscopy of thorium monoxide,ThO in support of Particle Physics Michael C. Heaven Dept. Chem., Emory University, Atlanta, Georgia, USA

Goals: a)permanent electric dipole moments a b)Franck-Condon prediction/intensity c)lifetime Outline II.Experimental setup IV.Analysis/Results III. Observation-Spectra a. Dispersed Fluorescence b. Lifetime (Decay curve) c. Stark V.Discussion I.Motivation VI.Summary a F. Wang, A. Lee, T.C.Steimle and M.C. Heaven, J.Chem. Phys, 134, (2011)

Motivation Needed in scheme to test of elementary particle physics beyond the Standard Model via measurement of electric dipole moment of electron, d e. Chemist’s view of an electron: Point Charge Physist's view of an electron: Point Charge with distribution Dipole moment of an electron, d e Experimental limit a : |d e | < 1.6  e  cm a B. Regan, E. Commins, C. Schmidt, D. DeMille, PRL 88, (2002) Based on thallium atom. Note dipole moment of HCl  6 D= 1.2   e.cm How big is d e ?Standard Model d e ~ e·cm times smaller

 Amplifying the electric field E int with a polar molecule Why ThO? Energy= -E int d e E int = electric field near the nucleus  Small  -doubling  The  =1 component of the 3  state is non-magnetic. Heavy polar molecular: Smaller systematic errors The metastable H 3  1 state : E int ~  2 Z 3 e/a 0 2 ~ 100 GV/cm  Polarizability factor Z: Atomic number complete polarization with very small fields

Experimental Setup Laser ablation source and supersonic expansion, Laser Induced Fluorescence (LIF) detector Well collimated molecular beam Metal target(Th foil) Pulse valve skimmer Ablation laser O 2 & Ar(carrier gas) Pulsed dye laser Single freq. tunable laser radiation Fluorescence PMT Monochromator PMT Stark plates Optical Stark spectroscopy Excitation spectra High resolution spectra Thorium foil O2O2 DF spectra

Observed electronic states and transitions in ThO G.Edvinsson and A. Lagerqvist(1985) E (0 + )  X 1  F(0 + )  X 1  F-H 3  613nm 545nm 760nm R-H 3  G-H 3  E&H same Th 2+ (7s6d)O 2− configuration a. a V.Goncharov, J. Han, L.A.Kaledin, and M.C.Heaven, J.C.P 122,204311(2005)

Pulsed Dye Laser Observation: Excitation & DF P-branch R-Branch cm -1 DF Spectra P-branch R-Branch cm -1 Excitation Spectra DF Spectra E (0 + ) <---X 1  (1,0) F    <---X 1  (0,0) ”” ’’ Laser ”” ’’

Lifetime measurement E (0 + ) -X 1  (  ) F (0 + ) -X 1  (  ) Laser decay Laser decay

High Resolution: R(0) E-X Field Free & Stark a c b E=0V/cmE=3600.7V/cm E=0V/cm E= V/cm

1) Franck-Condon factor prediction Prof. LeRoy’s Suite of Program: “RKR1 v2.0” & “Level v8.0”  1,01,11,21,3 E(0 + )-X 1   0,00,10,20,3 F(0 + )-X 1  (0,0) (0,1) F 1 (0 + ) -X 1  (  ) E 1 (0 + ) -X 1  (  ) (1,0) (1,1) (1,2) (1,3) Analysis/Results

Fit to: Four parameters:y0, A1, x0,  1  1 is lifetime 2) Radiative lifetime measurement E (0 + ) -X 1  (  ) F (0 + ) -X 1  (  )  1 =0.2594(5)  s  1 =0.574(9)  s Analysis/Results (Conti.)  1,0 (E-X) < 1.56 D  0,0 (F-X)≈0.95 D  i is radiative lifetime for the upper level, A  is the Einstein spontaneous emission coefficients,    is the transition dipole moment(Debye),   is the transition frequency(cm -1 ).

Analysis of FF & Stark Spectrum of E-X (1,0)  (case(a))  S  J  > Basis function: H Rot =BJ 2 Field-Free Spectrum  T 10 = (36) cm -1 ; B”= (27) cm -1 ; B’= (27) cm -1 Stark Spectrum  8  8 representation ( J=0-7)  (X 1  + ) = (12) D  (E(  + )) = (10) D

Discussion Permanent electric dipole moment Less Polarizable Theory a 1 3.9(CASSCF) Theory b (RCCSD(T)) a C. M. Marian, U. Wahlgren, O. Gropen, and P. Pyykko, THEOCHEM 46, 339 (1988). b A.A. Buchahenko,J. Chem. Phys. 133, (2010) Th 2+ (7s6d)O 2− Th 2+ (7s 2 )O 2−

Summary and Future work a)Franck-Condon prediction matches the experimental intensity pretty well. b)The lifetimes for F(0 + )-X 1  + (0,0) and E(0 + )-X 1  + (1,0) bands are measured. The transition moments were estimated for both bands. c) Dipole moments were determined for both E(0 + ) and X 1  + states. The dipole moment for the H 3  1 state will be approximately that of the E(0 + ) state because the two states are derived from the same Th 2+ (7s6d)O 2− configuration. d) Different production methods need to tried to pumping ThO molecules to the metastable H 3  1 state. (e.g. Dicharge source) e) Other thorium containing molecules can also be tried: ThC,ThSi.

Thank you!