The spectroscopy of bound and predissociatingudRydberg states of NO in external electric fields

摘要

This thesis reports the application of static and ramped electric fields to the Rydbergudstates of NO. Chapter 1 introduces the history of Rydberg states, their exoticudproperties, decay mechanisms, and the effect of an applied electric field. Chapter 2uddetails the experimental set-up used for the experiments presented in this thesis.udChapter 3 describes the structure of NO and multiphoton excitation scheme utilisedudfor the work presented in this thesis.udChapter 4 investigates the effect of applied DC electric fields in the rangeud0 – 150 V cm-1 on the predissociating Rydberg states of NO below the υ+ = 0udionisation limit, with principal quantum numbers n = 25 – 30. The Stark states areudaccessed by two-colour, double-resonance excitation via the υ′ = 0,N′ = 0, 1, 2, and 4udrovibrational states of the A2Σ+ state. The N (2D) atoms produced by predissociationudare measured by (2 + 1) resonance-enhanced multiphoton ionization. The zero fieldudand predissociation spectra are analysed using a matrix diagonalisation method. InudChapter 5, initial progress on simulating the spectra is presented. The predissociationudspectra are compared with pulsed-field ionization spectra of the bound Rydberg stateudpopulation providing an almost complete picture of the Rydberg state dynamics.udIn Chapter 6, ramped fields of varying slew rates are applied to the bound Rydbergudstates of NO, and the ionisation time profiles are obtained. The development of theudexperimental chamber and investigation into sources of electrical noise required toudachieve this is discussed. It is shown that the rotational quantum state composition ofudfield-ionised molecules can be controlled by varying the slew rate of the appliedudelectric field.