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Title: Time-dependent quantum dynamics of molecule predissociation
Author: Hussain, A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The work in this thesis uses wavepacket techniques on a discrete grid to solve the time-dependent Schroedinger equation numerically for a series of problems within the field of photodissociation dynamics. The systems studied focus on the phenomenon of 'predissociation', either electronically, via a non-adiabatic curve-crossing between (diabatically) bound and (diabatically) unbound Born-Oppenheimer potential energy surfaces (PESs), or vibrationally, in a system where there are several active vibrational modes, and the vibrational energy is enough to rupture one of the bonds provided enough can be concentrated in a single mode via intramolecular vibrational relaxation (IVR). The curve-crossing between the (bound) B and (repulsive) Y states of the I-Br molecule is studied in detail, being an example of electronic coupling that obeys neither the weak or strong limiting case. The dynamics of the B state are explored in detail, both via the propagation of coherent wavepackets, and by the propagation of the limiting (zero-coupling) vibrational eigenstates, to investigate the state-selectivity of the perturbation. It is found that the vibrational lifetimes vary dramatically with quantum number, with adjacent states often having half-lives that differ by two or three orders of magnitude. Finally, a series of calculations are performed simulating a set of pump-probe experiments that have been carried out on this system, and using the data previously generated on the B-state vibrational lifetimes to assist in the analysis. Qualitative agreement with experiment is achieved, and the data on vibrational lifetimes explains the main features of the ionisation traces; there is evidence that the model potentials (taken from the literature) are part of the explanation for any discrepancies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available