The high resolution technique of Stark quantum beat spectroscopy is used to examine the electric dipole moment function for the first excited singlet state (Ã 1A2) of formaldehyde-h2 and formaldehyde-d2. The high precision of these measurements (i.e., better than 5 parts in 104) enables detailed determination of a-axis dipole moment components (μa) for individual J = 2 rovibronic levels in the ν4 out-of-plane bending mode. In the case of 2 1,1 rotational levels, we find μa (40) = 1.4784(7) D and μa (41) = 1.4678(4) D for H 2CO. For D2CO the measured 21,1 dipole moments are μa (40) = 1.4698(6) D,μa(4 1) = 1.4693(3) D, and μae(43) = 1.4786(7) D. The state-specific variations in μa revealed by this study reflect the structural influences exerted by the pervasive S1∼ S0 nonadiabatic interactions and the pyramidally distorted equilibrium configuration which characterize the Ã state of formaldehyde. The origin and experimental manifestation of the out-of-plane dipole moment component (μc) in nonrigid Ã 1A2 formaldehyde is also discussed.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry