CORIOLIS-DEPENDENT STARK-EFFECT OF THE 2-NU(3) BAND OF METHANE OBSERVED BY SATURATED ABSORPTION-SPECTROSCOPY

We studied the vibration-induced dipole moment of methane by observing Stark-modulation spectra of the 2v(3) band centered at 1.66 mu m. The spectral purity of an external cavity semiconductor laser and radiati on density in a Fabry-Perot cavity absorption cell are sufficiently hi gh to record sub-Doppler saturated absorption lines with a spectral re solution of 0.8 MHz. First-order Stark shifts of the E-type symmetry c omponents in the P(2), Q(2), Q(4), Q(5), R(2), R(4), and R(5) transiti ons were measured, and the vibration-induced dipole moments for the v( 3)=2 State were determined. Their values clearly demonstrate the Corio lis-induced dipole term, yielding [5.79(5) + 0.440(18) x (2L - 3)] mD for the J(R) level, where L is defined to be - (R + 1), 0, and R for t he R = J-1, J, and J+1 levels, R and J are rotational and total angula r momentum quantum numbers, and numbers in parentheses are 90% confide nce intervals in unit of the last digit. (C) 1996 American Institute o f Physics.