Stuttgart 2012 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 14: Poster 2: Biomolecules, Electronic Spectroscopy, Experimental Techniques, Quantum Chemistry, Various Topics
MO 14.12: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.IV
Mulitiphoton ionization and fragmentation of HCl: A competition of different pathways leading to H+, Cl+, HCl+ and Cl−. — •Michael Schiller, Asylkhan Rakhymzhan, Alexey Chichinin, Sebastian Kauczok, Karl Heinz Gericke, and Christof Maul — Institut für phys. und theo. Chemie, TU Braunschweig, Germany
HCl exhibits a complex fragmentation and ionization behavior upon resonant photoexcitation of its Rydberg electronic states at around 10 eV. REMPI/TOF techniques and 3D Velocity Map Imaging were used to state selectively determine product yields and photoproduct kinetic energy and angular distributions. The total energy range is 15 to 20 eV, depending on a 3 or 4 photon excitation pathway with photons in the UV wavelength range. Special emphasis is laid on the intermediate state B1Σ+ which is reached via 2 photon absorption from the HCl ground state X1Σ+. This intermediate Rydberg state holds a double minimum potential due to the mixing among the V1Σ+ and E1Σ+ states. A further UV-photon initiates the competition between ionization and fragmentation processes. Repulsive Rydberg states are likely to cause the fragmentation and lead to slow H+ and Cl+ Ions. The competing pathways via an ion pair state or the ionic ground state lead to faster H+ Ions as well as to HCl+ and Cl−. An intriguing case is the Cl− anion resulting from the photodissociation of the neutral HCl precursor. Belonging to the ion-pair state, it has so far not been detected directly, but was assigned by the analysis of various V1Σ+ - X1Σ+ (v,0) transitions, which will also be regarded.