Sub-Doppler resolution Stark-modulation spectra of 20 transitions in the band of methane have been recorded using a difference-frequency-generation source referenced to an optical frequency comb with a frequency uncertainty of a few kilohertz. First-order Stark shifts in the vibrational excited () and ground states have been measured separately in the presence of an electric field up to 31 kV/cm. The observed spectra have been analyzed, taking into account the mixing of the vibration–rotation wave functions due to high-order vibration–rotation interactions. The permanent electric dipole moment constants induced by the vibration, rotation, and Coriolis-type terms in the state, and those induced by rotation in the vibrational ground state, are determined as , , , and .
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Numbers in parentheses indicate the uncertainties in units of the last digit. Note that the uncertainty of the electric field strength is not considered in .
Table 3.
Calculated Stark Shift Constants, , , and , Together with [27] for Comparison
−0.86603
−0.86603
0
−1.7321
0.19701
0.18558
−1.8870
1.8080
−0.12992
−0.10392
1.8922
−1.5214
−0.019857
−0.026243
1.1052
−0.37782
0.095916
0.081572
−4.3004
1.8068
0.0089684
0.010779
−1.1836
0.25544
−0.073290
−0.057171
4.4172
−1.5968
−0.016078
−0.019811
2.2335
−0.48182
0.28868
0.28868
0
−1.7321
−0.12989
−0.15588
−1.8922
1.0018
0.082401
0.10392
2.4998
−0.55055
0.024671
0.029457
0.75401
−0.30373
−0.075855
−0.099416
−4.6964
0.62358
−0.0076359
−0.013972
−0.42071
0.13149
0.053249
0.074111
4.4254
−0.42023
−0.052672
−0.041239
1.8870
0.79006
0.052926
0.037790
−3.6050
−1.1501
−0.038108
−0.028550
3.5464
0.97132
−0.014471
−0.0088370
1.4628
0.40850
0.042634
0.031839
−6.2382
−1.3945
Table 4.
Standard Deviations of the Least-Squares Fit in Kilohertz Unit for Three Kinds of and Three Sets of Adjustable Parametersa
Numbers in parentheses indicate the uncertainties in units of the last digit. Note that the uncertainty of the electric field strength is not considered in .
Table 3.
Calculated Stark Shift Constants, , , and , Together with [27] for Comparison
−0.86603
−0.86603
0
−1.7321
0.19701
0.18558
−1.8870
1.8080
−0.12992
−0.10392
1.8922
−1.5214
−0.019857
−0.026243
1.1052
−0.37782
0.095916
0.081572
−4.3004
1.8068
0.0089684
0.010779
−1.1836
0.25544
−0.073290
−0.057171
4.4172
−1.5968
−0.016078
−0.019811
2.2335
−0.48182
0.28868
0.28868
0
−1.7321
−0.12989
−0.15588
−1.8922
1.0018
0.082401
0.10392
2.4998
−0.55055
0.024671
0.029457
0.75401
−0.30373
−0.075855
−0.099416
−4.6964
0.62358
−0.0076359
−0.013972
−0.42071
0.13149
0.053249
0.074111
4.4254
−0.42023
−0.052672
−0.041239
1.8870
0.79006
0.052926
0.037790
−3.6050
−1.1501
−0.038108
−0.028550
3.5464
0.97132
−0.014471
−0.0088370
1.4628
0.40850
0.042634
0.031839
−6.2382
−1.3945
Table 4.
Standard Deviations of the Least-Squares Fit in Kilohertz Unit for Three Kinds of and Three Sets of Adjustable Parametersa