AI Article Synopsis
- The study employs velocity imaging and REMPI to analyze Br fragments from the photodissociation of various bromofluorobenzenes at 266 nm.
- The majority (over 96%) of the detected Br fragments are in the ground state (Br(2P3/2)), and their energy distributions reveal two dissociation pathways: a fast direct route and a slower one involving excitations along specific electronic states.
- The findings contrast with previous data from photofragment translational spectroscopy, highlighting significant discrepancies between analytical methods.
Article Abstract
Velocity imaging technique combined with (2 + 1) resonance-enhanced multiphoton ionization (REMPI) has been used to detect the Br fragment in photodissociation of o-, m-, and p-bromofluorobenzene at 266 nm. The branching ratio of ground state Br(2P3/2) is found to be larger than 96%. Its translational energy distributions suggest that the Br fragments are generated via two dissociation channels for all the molecules. The fast route, which is missing in p-bromofluorobenzene detected previously by femtosecond laser spectroscopy, giving rise to an anisotropy parameter of 0.50-0.65, is attributed to a direct dissociation from a repulsive triplet T1(A' ') or T1(B1) state. The slow one with anisotropy parameter close to zero is proposed to stem from excitation of the lowest excited singlet (pi,pi*)state followed by predissociation along a repulsive triplet (pi,sigma*) state localized on the C-Br bond. For the minor product of spin-orbit excited state Br(2P1/2), the dissociating features are similar to those found in Br(2P3/2). Our kinetic and anisotropic features of decomposition obtained in m- and p-bromofluorobenzene are opposed to those by photofragment translational spectroscopy. Discrepancy between different methods is discussed in detail.
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| http://dx.doi.org/10.1021/jp710212r | DOI Listing |
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