Laser-induced fragmentation fluorescence detection of the vinyl radical and acetylene

When excited at λ=230 nm, the vinyl radical and acetylene may be detected via fluorescence from C2(d3Πg→a3Πu) using laser-induced fragmentation fluorescence (LIFF). Vinyl photodissociation creates C2(d3Πg) more efficiently than acetylene photodissociation by a factor of 1300–200 depending on the internal excitation of the vinyl radical. The key difference in LIFF efficiency between the two molecules depends on the mechanism for loss of the first H atom. This LIFF process may provide a method for probing the elusive vinyl radical in methane flames.