The 365 nm 41 0 (υ′= 0 - υ4″ = 1) band in the A 1A2 - X1A1 absorption system of formaldehyde-d2, D2CO, has been studied under high resolution. Rotational analysis procedures, which include approximations allowing for strong Coriolis perturbations to the υ4″ = 1 level, are described and compared with more rigorous approaches. Rotational constants for both ground and excited vibronic states are determined by least-squares analysis, and significantly revised ground state vibrational frequencies reported, as follows: ν4″ = 936.5 ± 0.1 cm-1, ν6″ = 989.3 ± 0.1 cm-1. The coupling parameter ξ64 a (2̃Aζ64 a), associated with the a-axis Coriolis interaction between υ4″ = 1 and υ6″ = 1 levels, is determined to be |ξ64 a| = 4.98 ± 0.02 cm-1. Several resonant Coriolis perturbations, arising from accidental coincidences between certain ν4 rovibrational levels and levels of ν6 and ν3, are discussed and characterized. A simple theory for the intensity distribution in a pair of Coriolis-coupled vibronic bands is used to relate minor intensity anomalies observed in the 41 0 band to the apparent absence of the adjacent 61 0 band.
|Number of pages||17|
|Journal||Spectrochimica Acta Part A: Molecular Spectroscopy|
|Publication status||Published - 1974|