Double-resonance spectroscopy of radicals: higher electronic excited states of 1- and 2-naphthylmethyl, 1-phenylpropargyl and 9-anthracenylmethyl

摘要

Multiple pulsed-laser frequencies are used to extract the excitation spectra of D-n <- D-0 transitions (n > 1) of the 1- and 2-naphthylmethyl, 1-phenylpropargyl and 9-anthracenylmethyl radicals. Bands are, respectively, observed at 27993, 27478, 32437 and 25063cm(-1), with respective widths (at half maximum) of 292, 290, 149 and 326cm(-1). On the basis of comparison with ab initio vertical excitation energies, the transitions for 2-naphthylmethyl, 1-phenylpropargyl and 9-anthracenylmethyl radical are assigned as D-3 <- D-0. The observed transition of 1-naphthylmethyl is ambiguously either or both D-3 <- D-0 and D-4 <- D-0. From the wide Lorentzian profiles observed, lifetimes of a few tens of fs are inferred, the spectral widths precluding this class of molecule from being responsible for the long-unidentified diffuse interstellar bands.