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Vibrational predissociation in weakly bound molecules

Krause, Paul James; (1999) Vibrational predissociation in weakly bound molecules. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

A time-dependent quantum mechanical approach is used to study the vibrational predissociation of small weakly bound complexes. The vibrational predissociation process involves the breaking of one or two weak intermolecular bonds. Information such as the vibrational predissociation lifetimes and product distributions are extracted from the evolving wavepacket and compared with previous theoretical calculations and experimental results when available. Dynamical information about the process can also sometimes be obtained from studying the wavepacket at various time intervals. Three-atom complexes of the type XBC, where X is a closed shell atom and BC is a diatomic molecule are studied (for example NeCl2, HeCl2, NeICl, HeICl and HeBr2). In the studies on HeBr2 we obtain a good agreement with both previous theoretical and experimental results. Two types of four-atom complexes are studied. The first type is an extension of the three-atom complexes studied in which there is an additional closed shell atom and can be expressed as X2BC (for example Ne2Cl2, He2Cl2, Ne2Br2 and He2Br2). The first theoretical studies on X2Br2 complexes show that they dissociate via a sequential mechanism like that of the X2Cl2 complexes. The second type is of the form A2-BC, where A2 and BC are homonuclear and heteronuclear diatomics, respectively (for example D2-HF, H2-HF, D2-OH and H2-OH). We have developed for H2-HF an improved potential energy surface based on ab initio computations and find that it gives very similar results to that of the previous surface. Finally, comparison with experiment for H2-OH has given the first insights into the mechanism of decay for this system. It is found that the time-dependent wavepacket approach is a useful method for studying the vibrational predissociation of weakly bound complexes.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Vibrational predissociation in weakly bound molecules
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Predissociation
URI: https://discovery.ucl.ac.uk/id/eprint/10103059
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