The emission spectrum of the 1B 1(π *-n +) state of 1,2-cyclobutanedione excited at 488.0 nm

Abstract

The spectrum of the emission from the 1B 1(π *-n +) state of 1,2-cyclobutanedione excited at 488.0 nm has been measured. Wavelengths and vibrational assignments are reported for 24 bands between 490 and 550 nm, 12 of which can be identified with hot bands in the absorption spectrum. Prominent bands in the emission spectrum are associated with excitation of V '' 8, the symmetric in-plane carbonyl bend (281 cm −1); v '' 12, the asymmetric carbonyl wag (488 cm −1); and v '' 7, a symmetric ring distortion (522 cm −1). Sequences in v 13, the ring-twisting vibration, are also prominent; the initial excitation lies in the 13 3 3 absorption band, while the emission shows intensity maxima for v ' 13 = 0 and 2, and a bimodal vibrational relaxation is suggested.