Triatomic Hydrogen
Welcome to the Triatomic Hydrogen Group at the Department of Molecular and Optical Physics - University of Freiburg, Germany

Predissociation of H3 Rydberg states
I. Mistrik, R. Reichle, H. Helm and U. Müller
Department of Molecular and Optical Physics, Albert-Ludwigs-Universität, Hermann-Herder-Strasse 3, D-79104  Freiburg, Germany


A fast-beam spectrometer is used to investigate the photofragmentation and autoionization dynamics of laser-excited triatomic hydrogen molecules. The yield of neutral products from rapidly predissociated states of H3 is monitored in parallel with the field ionization signal. Using this spectrometer, we have measured the natural lifetime of low principal quantum number Rydberg states nsA 1´ and npE´. For the 3sA 1´, 4sA 1´, and 5sA 1´ electronic states, we find lifetimes decreasing with increasing principal quantum number. This is unexpected for a Rydberg series and confirms the observations of a previous investigation. In addition, our experiments give direct evidence that even very high principal quantum number Rydberg states of H3 are selectively subject to strong predissociation. This process appreciably shortens their natural lifetimes. In the high principal quantum number ns- and nd Rydberg series converging to the lowest ionization threshold of H3 we find a significant variation of the predissociation yield with principal quantum number and electronic angular momentum. Windows with enhanced predissociation in the Rydberg series are explained by nonadiabatic couplings of the laser-prepared initial states with the repulsive ground states surface mediated by vibrationally degenerate mode excited 4pE ´ and 5pE´ states. The relevance of the H3 predissociation mechanisms for the dissociative recombination of H 3+ is discussed. ©2001 The American Physical Society

©2001 Phys. Rev. A, 63, 042711 (2001)

PACS: 33.80.Gj, 33.80.Rv, 34.80.Ht

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