PULSED-FIELD IONIZATION SPECTROSCOPY OF CO VIA THE E(1)PI STATE AND NO VIA THE B-2-PI STATE

The pulsed-field ionization (PFI) spectra of CO and NO are recorded us ing stepwise two-colour multiphoton excitation with ion detection. The se spectra demonstrate the production of CO+ and NO+, state-selected i n unique vibration-rotation levels. For CO a (2 + 1') excitation proce ss is employed via the E(1) Pi (upsilon' = 0) state, whereas for NO a (1 + 1') process is used via the B-2 Pi (upsilon' = 4) state. The one- colour REMPI spectrum of NO via this same state is also reported for t he first time. The NO spectrum involves a nominal two-electron excitat ion in the final step and the intensity is derived from configuration interaction with the C-2 Pi. Rydberg state. The PFI spectrum of CO sho ws marked differences in rotational intensities compared to those dete rmined by Fujii et al. in direct ionization [1]. The effects of final state interactions are abundant in both spectra, with the observation of window resonances and intensity enhancements, including some unexpl ained enhancements of positive N+ - J' lines in CO.