Franck-Condon factors of the torsional mode ν7 in the SVL emission of glyoxal

Drastic changes occur in the intensity pattern of the emission spectra of the 7ⁿ-levels as compared to the spectrum of the 0⁰-level. These changes are due to greatly enhanced intensity of the sidebands in the progression of the 7-vibration. This enhancement is, in a first approximation, in agreement with calculations of the Franck-Condon factors of these transitions. The additional intensity of the sidebands in the emission from the 7²-level can be explained in part by intensity borrowing from the 5¹-emission due to a coupling of the 7² and 5¹-levels. The large relative intensities of the 7₅², 7₅³, and 7₇³ emission bands remain unexplained.