Pump/Probe Microwave-Optical Double Resonance (PPMODR) Study of Tungsten Carbide( WC) a and Platinum Carbide(PtC) b Funded by Fang Wang, Chengbing Qin, Ruohan Zhang, Timothy C. Steimle Dept. Chem. & BioChem.,Arizona State University, Tempe, AZ,USA Funded by b C. Qin, R. Zhang, F. Wang, T. C. Steimle, Chemical Physics Letters, 535, 2012 a F. Wang and T.C. Steimle, J. Chem. Phys. 136, (2012). International Symposium on Molecular Spectroscopy 67 th meeting

Outline I.What is PPMODR? a). History & Motivation b). Concepts & Experimental Set-up a). WC (X 3  1 ) II.Examples  -doubling parameter Observe nearly equal intensity (Magnetic dipole transition VS Electric dipole transition) b). PtC (X 1  + ) Nuclear spin-rotation interaction parameter 182 W (26.3%), 183 W (14.3%), and 184 W (30.1%), 186 W (28.6%) 194 Pt(33.0%, 195 Pt(33.8%) and 196 Pt (25.2%)

PPMODR(History) W.J. Childs, Physics Reports, 211(1992) Review of Laser-Radiofrequency double resonance studies S.D.Rosner, T. D.Gaily, and R. A. Holt, Phys. Rev. Lett. 35, 785 (1975) Molecular-beam, laser-radiofrequency double-resonance(LRDR) technique Precise ground-state data W. Ertmer and B. Hofer, Z Phys. A 276, 9(1976) Hyperfine structure measurements of the atomic beams using the LRDR technique W.J. Childs, L.S. Goodman: Phys. Rev. A 21, 1216 (1980) Hyperfine constants of highest precision with the molecular beam using using LRDR technique W. E. Ernst and S. Kindt, Appl. Phys. B 31( 1983) A laser-Microwave double-resonance experiment has been developed

L I0I0 I Absorption The intensity is given by Beers Law: I=I 0 e -  LC ≈I 0 (1-  LC)Absorption≈  LC  is molecular absorption coefficient C is the concentration  ∝ f*  2 f is the fraction of the total which is in the lower of the two states.  is the transition frequency Laser or Radio-frequency Line width  v ∝  Optical spectroscopy & Microwave spectroscopy High sensitivity, resolution, selectivity PPMODR(Motivation) Pump/Probe Microwave-Optical Double Resonance High absorption High sensitivity Optical spectroscopy High sensitivity, low resolution Microwave spectroscopylow sensitivity, high resolution

Optical spectroscopy pump Microwave radiation skimmer Well collimated molecular beam Single freq. tunable laser radiation PMT Gated photon counter W rod or Pt rod Pulse valve Ablation laser CH4(5%) & Ar PPMODR(Concept) J” J’ h  laser Excitation J” Radio-frequency repopulate

Frequency Sythesizer(0~20GHz) Rubidium frequency standard homemade E-field horn antenna(3cmX0.4cm) Active Frequency multiplier 4X or 2X Magnetic sheild box FWMH: 50kHz with<<1mW power PPMODR(Experimental) Microwave Radiation Source Pump beam~200mW Probe beam (~20mW) Laser induced fluorescence(LIF)

Examples 1WC Electron electric dipole moment(eEDM) Measurement WC: 1 J. Lee, E.R. Meyer, R. Paudel, J.L. Bohn and A.E. Leanhardt, J. Mod. Opt. 56, 2005, (2009).  -doubling õ Δ ~1kHz 2 F. Wang and T.C. Steimle, J. Chem. Phys. 134, (2011).  -doubling õ Δ <2MHz Prediction Optical Spectroscopy - J=1 J=2 X 3  1 (v=0) - + Microwave Frequency(~60GHz) WC +  -Doubling

WC – Spectra with PPMODR LIF A - J=1 J=2 X 3  1 (v=0) [17.6]2(v=1) +/- J=3 CBD Microwave power:10mW FWHM:400kHz 1.54MHz 2.31MHz  -doubling õ Δ =0.385(13)MHz

Why I mag. ≈ I elec. ? A.Magnetic dipole transition probability(X 3  1 ) B.Mix two nearly degenerate energy levels due to stray electric field (  -doublet) Possible reasons:

I mag. ≈ I elec. Rabi frequency  elec. = 2  ab (elec.)*Efield/h a b I mag should be small. Microwave power 10mW Area=1.0 cm 2 Transit time t=30  s  ab (elec.)=3.90D=1.30* C m  =3.3*10 -7 J/m 3 Energy density  Rabi  t≥1 (Rabi frequency and transit time) Rabi frequency  mag.. = 2  ab (mag.)*Bfield/h A.Magnetic dipole transition probability (X 3  1 )  ab (mag.)=(g L  +g s  )  B =0.022  B =2.04* J/T Magnetic dipole moment:  =2,  =-1, g L  +g s  Electric dipole moment: E-field=273.0V/m B-field=9.1*10 -7 T Rabi cycles

A.Magnetic dipole transition probability (X 3  1 ) 0.1% mixing of the nearly degenerate  -doublet levels - J=1 X 3  1 (v=0) MHz

. Ψ N =C + Ψ + + C - Ψ - Basis function |  JM J > E stray ≈ 0.05V/cm Ψ N - =-0.999Ψ Ψ + Ψ N + =0.032Ψ Ψ *100% ≈ 0.1% B.Mix two energy levels due to stray electric field (J=1,  - doublet) How big is the stray electric field for 0.1% mixing?  =3.9D

Experimental Pt bonding investigation: nuclear spin-rotation interaction Examples 2PtC 195 PtCX 1  + (v=0) 3/2 J=1 J=2 1/2 3/2 5/2 Microwave Frequency(~60GHz) 195 Pt(I=1/2) J=0 1/2 F Microwave Frequency(~30GHz)

PtC – Spectra with PPMODR 3/2 J=1 J=2 X 1  + 1/2 3/2 5/2 A 1  5/2 J=3 7/2 LIF 195 PtC(I=1/2) A 195 PtC A C i eff =0.138(12)MHz

Summary PPMODR has been implemented. Precise W-doubling parameter has been determined Unusual intensity observed. Possible reasons have been addressed. Spin-rotation interaction parameter has been determined WC PtC Future Plans: AuX, ThX (X=C, F,O,S)