The spectroscopy of bound and predissociating Rydberg states of NO in external electric fields

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