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International Symposium on Molecular Spectroscopy 67th meeting Pump/Probe Microwave-Optical Double Resonance (PPMODR) Study of Tungsten Carbide( WC)a and Platinum Carbide(PtC)b Fang Wang, Chengbing Qin, Ruohan Zhang, Timothy C. Steimle Dept. Chem. & BioChem.,Arizona State University, Tempe, AZ,USA aF. Wang and T.C. Steimle, J. Chem. Phys. 136, 044312 (2012). Funded by bC. Qin, R. Zhang, F. Wang, T. C. Steimle, Chemical Physics Letters, 535, 2012 Funded by Outline I. What is PPMODR? a). History & Motivation b). Concepts & Experimental Set-up II.Examples a). WC (X3D 1) 182W (26.3%), 183W (14.3%), and (30.1%), 186W (28.6%) 184W W-doubling parameter Observe nearly equal intensity (Magnetic dipole transition VS Electric dipole transition) b). PtC (X1S+) 194Pt(33.0%, 195Pt(33.8%) and 196Pt (25.2%) Nuclear spin-rotation interaction parameter PPMODR(History) Precise ground-state data S.D.Rosner, T. D.Gaily, and R. A. Holt, Phys. Rev. Lett. 35, 785 (1975) Molecular-beam, laser-radiofrequency double-resonance(LRDR) technique 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 W.J. Childs, Physics Reports, 211(1992) Review of Laser-Radiofrequency double resonance studies PPMODR(Motivation) Absorption Laser or Radio-frequency I0 L The intensity is given by Beers Law: I=I0e-aLC≈I0(1-aLC) Absorption≈aLC High absorption a∝f*u2 Line width Dv∝u Optical spectroscopy I a is molecular absorption coefficient C is the concentration High sensitivity f is the fraction of the total which is in the lower of the two states. u is the transition frequency High sensitivity, low resolution Microwave spectroscopy low sensitivity, high resolution Optical spectroscopy & Microwave spectroscopy High sensitivity, resolution, selectivity Pump/Probe Microwave-Optical Double Resonance PPMODR(Concept) Optical spectroscopy Gated photon counter PMT Ablation laser Pulse valve skimmer CH4(5%) & Ar W rod or Pt rod Excitation pump J’ hulaser J” Microwave radiation Single freq. tunable laser radiation repopulate Radio-frequency Well collimated molecular beam J” PPMODR(Experimental) Microwave Radiation Source FWMH: 50kHz with<<1mW power Rubidium frequency standard Frequency Sythesizer(0~20GHz) Laser induced fluorescence(LIF) Active Frequency multiplier 4X or 2X homemade E-field horn antenna(3cmX0.4cm) Magnetic sheild box Probe beam (~20mW) Pump beam~200mW Examples 1 WC WC: Electron electric dipole moment(eEDM) Measurement 1J. Lee, E.R. Meyer, R. Paudel, J.L. Bohn and A.E. Leanhardt, J. Mod. Opt. 56, 2005, (2009). W-doubling õΔ~1kHz Prediction 2F. Wang and T.C. Steimle, J. Chem. Phys. 134, 201106 (2011). W-doubling õΔ<2MHz Optical Spectroscopy WC X3D1 (v=0) J=2 + - Microwave Frequency(~60GHz) J=1 - + W-Doubling WC – Spectra with PPMODR Microwave power:10mW FWHM:400kHz J=3 [17.6]2(v=1) +/- LIF J=2 + - A B C D J=1 + X3D1 (v=0) W-doubling õΔ=0.385(13)MHz 2.31MHz 1.54MHz Why Imag. ≈ Ielec.? Possible reasons: A. Magnetic dipole transition probability(X3D1) B. Mix two nearly degenerate energy levels due to stray electric field (W-doublet) A. Magnetic dipole transition probability (X3D1) Imag. ≈ Ielec. Rabi cycles wt≥1 (Rabi frequency and transit time) Rabi frequency wmag..=2p*mab(mag.)*Bfield/h b wRabi Rabi frequency welec.=2p*mab(elec.)*Efield/h a Magnetic dipole moment: mab(mag.)=(gLL+gsS)mB=0.022mB=2.04*10-25J/T Electric dipole moment: Energy density r E field Bfield P Area c 2r 0 Efield c L=2,S=-1, gLL+gsS0 mab(elec.)=3.90D=1.30*10-29C m r=3.3*10-7 J/m3 Microwave power 10mW Area=1.0 cm2 Transit time t=30ms E-field=273.0V/m B-field=9.1*10-7 T w elec . t 1009.0 w t 0.018 1 Imag should be small. m ag . A. Magnetic dipole transition probability (X3D1) w elec . w t 1009.0 m ag . t 0.018 1 J=1 X3D1 (v=0) 0.1% mixing of the nearly degenerate W-doublet levels + 1.54MHz B. Mix two energy levels due to stray electric field (J=1, Wdoublet) . How big is the stray electric field for 0.1% mixing? H 11 H 21 H 12 1.54 H 22 0.9818 E stray H 12 H 21 ( M H z ) ΨN=C+Ψ++ C-Ψ- 0.9818 E m ( D ) E (V / cm ) M J W J J 1 Basis function |LSWJMJ> stray 0 ΨN-=-0.999Ψ--0.032Ψ+ ΨN+=0.032Ψ--0.999Ψ+ 0.0322*100%≈0.1% 0.50348 m=3.9D Estray ≈0.05V/cm Examples 2 PtC Experimental Pt bonding investigation: nuclear spin-rotation interaction 195PtC X1S+ (v=0) F J=2 5/2 3/2 Microwave Frequency(~60GHz) J=1 J=0 3/2 1/2 Microwave Frequency(~30GHz) 1/2 195Pt(I=1/2) PtC – Spectra with PPMODR 195PtC(I=1/2) A 1P J=3 195PtC 5/2 7/2 A LIF 5/2 J=2 A 3/2 1/2 J=1 Cieff=0.138(12)MHz 3/2 X 1S + Summary PPMODR has been implemented. WC Precise W-doubling parameter has been determined Unusual intensity observed. Possible reasons have been addressed. PtC Spin-rotation interaction parameter has been determined Future Plans: AuX, ThX (X=C, F,O,S)