The vinyl radical, ((A)over-tilde-(2)A ''<-(X)over-tilde-(2)A ') spectrum between 530 and 415 nm measured by cavity ring-down spectroscopy

High resolution (0.008 nm) transient absorption spectra have been measured for the vinyl radical (C2H3) (A) over tilde(2)A"<--(X) over tilde(2)A' tran sition between 530 and 415 nm using cavity ring-down laser absorption spect roscopy. This is over 200 times better resolution than the only previous re corded spectrum of vinyl in this wavelength region by Hunziker, Kneppe, McL ean, Siegbahn, and Wendt [Can J. Chem. 61, 993 (1983)]. With the improved r esolution in the present study, new vibrational bands are detected, and som e rotational structure of the bands is resolved. A calculation of the envel ope of the origin band was carried out, using a model for a c-type transiti on of an asymmetric top. For a best fit to the data, the model requires a 1 cm(-1) Lorentzian linewidth, which suggests a short-lived excited state. ( C) 1999 American Institute of Physics. [S0021-9606(99)02604-5].