Photodissociation yield spectroscopy of vinyl bromide cation generated by mass-analyzed threshold ionization:Vibrational spectroscopy and decay dynamics in the B state

摘要

A new technique[mass-analyzed threshold ionization(MATI)-photodissociation yield spectroscopy]to probe bound excited states of a cation was developed,which measures photodissociation yield of the cation generated by mass-analyzed threshold ionization.A vibrational spectrum of vinyl bromide cation in the B state was obtained using this technique.Optical resolution in the low vibrational energy range of the spectrum was far better than in conventional MATI spectra.The origin of the B state was found at 2.2578+-0.0003 eV above the first ionization onset.Almost complete vibrational assignment was possible for peaks appearing in the spectrum.Analysis of time-of-flight profiles of C2H_3~+product ion obtained with different laser polarization angles suggested that photoexcited vinyl bromide cation remained in the B state for several hundred picoseconds prior to internal conversion to the ground state and dissociation therein.