Knowledge Bank

Multiphoton excitation of ketene, $CH2CO$, with 193 nm radiation produces intense fluorescence form the $A\to X$ and $B\to X$ transitions of CH radical. Weaker emission is observed with use of 308 nm radiation. Infrared multiphoton dissociation of acetylbromide, $CH3C$(O)Br, produces luminescence very similar to that arising from ketene. These observations represent one of few cases of observation of ultraviolet emission following infrared multiphoton excitation of a ground state species, and supports a previous suggestion of a ketene intermediate in acetylbromide dissociation.