Extensive Measurements of VibrationInduced Permanent Electric Dipole Moments

Extensive Measurements of Vibration-Induced Permanent Electric Dipole Moments of Methane Keio University, JST ERATO Shoko OKUDA and Hiroyuki SASADA

Methane is a polar molecule! v 3 = 1 v 3 = 0

Methane is a polar molecule! v 3 = 1 v 3 = 0 A. C. Luntz and R. G. Brewer, J. Chem. Phys. 54, 3641 (1971), Fig. 1

Methane is a polar molecule! v 3 = 1 A. C. Luntz and R. G. Brewer, J. Chem. Phys. 54, 3641 (1971), Fig. 1 v 3 = 0 I. Ozier, Phys. Rev. Lett. , 27, 1329 (1971)

Methane is a polar molecule! Mid-infrared sources with a broad tunable range, high power, and narrow linewidth have been developed only recently. v 3 = 1 A. C. Luntz and R. G. Brewer, J. Chem. Phys. 54, 3641 (1971), Fig. 1 v 3 = 0 I. Ozier, Phys. Rev. Lett. , 27, 1329 (1971)

Methane is a polar molecule! Mid-infrared sources with a broad tunable range, high power, and narrow linewidth have been developed only recently. Optical Frequency Comb

Stark effects of methane J ’R 34 J’ = 3 33 v 3 = 1 32 23 J’=2 22 21 12 11 10 J ’= 1 v 3 = 0 J”=2 J ”R 22

Stark effects of methane J ’R 34 J’ = 3 the first-order Stark shifts 33 v 3 = 1 32 23 J’=2 ～ 20 MHz @ 10 k. V/cm 22 21 12 11 10 J ’= 1 v 3 = 0 J”=2 J ”R 22 ～ 600 k. Hz @ 10 k. V/cm

Setup 3. 3 μm, about 1 m. W electrodes gap ：(2. 000 ± 0. 005) mm interaction length： 108 cm sample pressure：about 10 m. Torr applied voltage：< 6200 V

Setup 3. 3 μm, about 1 m. W electrodes gap ：(2. 000 ± 0. 005) mm interaction length： 108 cm sample pressure：about 10 m. Torr applied voltage：< 6200 V sub-Doppler resolution about 200 k. Hz

Setup Optical Frequency Comb 3. 3 μm, about 1 m. W uncertainty in frequency determination about 10 k. Hz (short time average) electrodes gap ：(2. 000 ± 0. 005) mm interaction length： 108 cm sample pressure：about 10 m. Torr applied voltage：< 6200 V sub-Doppler resolution about 200 k. Hz

Setup sweep Optical Frequency Comb 3. 3 μm, about 1 m. W uncertainty in frequency determination about 10 k. Hz (short time average) electrodes gap ：(2. 000 ± 0. 005) mm interaction length： 108 cm sample pressure：about 10 m. Torr applied voltage：< 6200 V sub-Doppler resolution about 200 k. Hz

Observed transitions F. Adler et al. , Opt. Express, 18, 21861 (2010), Fig. 2

Stark shifts in the vibrational ground state

Stark shifts in the vibrational ground state cross-over resonance

ref: A. Dorney et al. , J. Mol. Spectrosc. , 42, 135 (1972)

A. Dorney et al. , J. Mol. Spectrosc. , 42, 135 (1972)

Prot'' /μD 25 24 23 22 A. Dorney et al. , J. Mol. Spectrosc. , 42, 135 (1972) 21 1 2 3 4 5 J'' 6 [1] I. Ozier, Phys. Rev. Lett. , 27, 1329 (1971), [2] E. H. Wishnow al. , J. Quant. Spectrosc. Ra. , 103, 102 (2007) 7 8 9

Prot'' /μD 25 24 23 22 A. Dorney et al. , J. Mol. Spectrosc. , 42, 135 (1972) Stark effect[1] 21 1 2 3 4 5 J'' 6 [1] I. Ozier, Phys. Rev. Lett. , 27, 1329 (1971), [2] E. H. Wishnow al. , J. Quant. Spectrosc. Ra. , 103, 102 (2007) 7 8 9

Coriolis interaction

0 -5 Pvib/m. D -10 -15 -20 -25 -30 Coriolis interaction -35 0 1 2 3 4 5 6 7 8 J'

J’R v 3 = 1 , J’ = 3 34 33 32

J’R v 3 = 1 , J’ = 3 34 33 32 least squares fit to the existing accurate data (standard deviation) ~ 10 MHz

PEDM of methane [up to the Coriolis term]

PEDM of methane least squares fit to the obtained shift data

PEDM of methane least squares fit to the obtained shift data − 16. 69(5) m. D 19. 6(6) μD 5. 1(8) μD 57 k. Hz

PEDM of methane -15 -16 Pvib/m. D -17 -18 -19 -20 -21 0 1 2 3 4 5 6 7 8 J' [calculation]

Conclusion

Permanent electric dipole moments