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MO: Molekülphysik
MO 26: Poster: Photochemistry
MO 26.1: Poster
Dienstag, 14. März 2006, 16:30–18:30, Labsaal
The role of superexcited stated in photoionization and photofragmentation of HCl — •Christof Maul1, Karl-Heinz Gericke1, and Alexey Chichinin1,2 — 1Institut für Physikalische und Theoretische Chemie, TU Braunschweig, 38106 Braunschweig, Germany — 2Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, 630090 Novosibirsk, Russia
HCl is known for competition of ionization and fragmentation when excited by two-photon absorption from its ground state X1Σ+ into the B1Σ+ state. The competition between fragmentation and ionization is initiated by absorption of a third photon, yielding either HCl+ or electronically excited H* and Cl* fragments. These species will produce H+ and Cl+ by absorption of a fourth photon. Besides the ground ionic state X2Π a multitude of neutral, mostly Rydberg, states are accessible by absorption of the third photon. These Rydberg states are called superexcited if they lie at higher energies than the molecular ionization potential.
Observing speed and spatial distributions of H+, Cl+, and HCl+, one can determine the nature of the states accessed after absorption of the third photon. The B1Σ+ state which is produced in the first two-photon absorption step, is unique in that it exhibits a pronounced double minimum well which results in an extremely broad range of internuclear distances for absorption of the third photon. This allows to also access repulsive Rydberg states which we believe to be the major contributors to the fragmentation channels, while ionization is likely to be due to a combination of direct and autoionization processes.