High Precision Dipole Moments in A 1(A2) Formaldehyde Determined via Stark Quantum Beat Spectroscopy

摘要

The high resolution technique of Stark quantum beat spectroscopy is used to examine the electric dipole moment function for the first excited singlet state (A1 A2) of formaldehyde-h2 and formaldehyde-d2. The high precision of these measurements enables detailed determination of alpha-axis dipole moment components mu(a) for individual J = 2 rovibronic levels in the V4 out-of-plane bending mode. In the case of 2(1,1) rotational levels, we find mu(a) 4 to the 0 power = 1.4784 (7) D and mu(a) 4 to the 1st power = 1.4678 4 to the 1st power D for H2CO. For D2CO the measured 2(1,1) dipole moments are mu(a) 4 to the 0 power = 1.4693 (3) D, and m(u) 4 to the 3rd power =1.4786(7) D. The state-specific variations in mu(a) revealed by this study reflect the structural influences exerted by the pervasive S(1) = S(0) nonadiabatic interactions and the pyramidally distorted equilibrium configuration which characterize the A state of formaldehyde. The origin and experimental manifestation of the out-of-plane dipole moment component mu(c) in nonrigid A 1A2 formaldehyde is also discussed. Reprints. (AW)