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MO: Molekülphysik
MO 9: Photoelektronenspektroskopie
MO 9.8: Vortrag
Montag, 22. März 2004, 18:15–18:30, HS 332
Photodissociation studies of state-selected molecular ions by velocity map ion imaging — •N. Hendrik Nahler, Olivier P.J. Vieuxmaire, Josephine A. Jones und Michael N.R. Ashfold — University of Bristol, School of Chemistry, Bristol BS8 1TS, UK
High resolution ion imaging methods have been used to study the photodissociation of ground state Br2+ (2Πg) and BrCl+ (2Π) cations, with spin-orbit state specification, monitoring 79Br+ and 35Cl+ fragments as appropriate. The state-selected molecular ions are prepared by a 2+1 REMPI scheme and than dissociated by absorption of a single photon from a second tunable dye laser. Image analysis allows precise determination of the dissociation energies of Br2+ (2Π3/2,g), Br2+ (2Π1/2,g), BrCl+ (2Π3/2), and BrCl+ (2Π1/2) and values for the respective spin-orbit splitting constants. The values so derived for BrCl+ are in excellent accord with those obtained from complementary photoelectron imagin studies.
Photoexcitation of Br2+ at wavelengths just above the first dissociation threshold yields ground state Br+ and Br fragments, the recoil anisotropy of which is found to be sensitively wavelength dependent. Careful measurements of the angular anisotropy (β-parameter) versus the dissociation wavelength reveals the presence of high frequency structure, in the region up to the first excited [Br(2P3/2) + Br+(3P1)] dissociation limit; this we attribute to predissociating vibrational levels in an adiabatic potential converging to this excited limit. The dissociation channels from BrCl+ show predominantly parallel character. Branching ratios into the various Br+ (3PJ) and Cl (2PJ) channels will be presented and discussed in the context of the various participating excited state potentials.