Lazenby, D.T.C.; (2011) The spectroscopy of autoionising and predissociating Rydberg states of NO. Masters thesis , UCL (University College London).

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Abstract

We employ a 2-colour multi-photon excitation scheme to excite autoionising and predissociating Rydberg states of NO converging to the \upsilon^+ = 1,N^+ = 0 ionisation limit of the molecular ion via the A^2\Sigma^+|\upsilon\primeN\prime=0 intermediate. In this energy region there is competition between autoionisation and predissociation and we monitor the fragments from both decay processes in an effort to study such competition; the NO+ ions from the ionisation route are detected directly and a second (2+1) REMPI scheme is used to probe the N(2D) dissociation product. By least squares fitting of the Fano formula to the experimental data we derive linewidths, \Gamma , shape indexes, q, and lifetimes, \tau , for selected resonances from the dominant np(0) and nf(2) Rydberg series present and assess qualitatively the variation in each throughout the spectrum. At several points in the spectrum where there is near resonance between the many Rydberg series present, we observe interferences between the decay pathways in which increased flux through one channel is accompanied by suppression in the other. The experimental data recorded here is studied alongside earlier work in the group on Rydberg states converging to the \upsilon^+ = 0,N^+ = 0 ionisation limit where dissociation is the only available (non-radiative) decay path. By least-squares fitting of the Fano formula to the experimental data, linewidths are derived and the effect of a vibrationally active core upon the predissociation dynamics is investigated.

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