ROTATIONAL PROPENSITIES IN THE STATE SELECTION OF NH3-FIELD IONIZATION( BY PULSED)

NH3+ ions have been prepared in unique vibration-rotation states v(2)( +), N+, K+, by pulsed-field ionization of high Rydberg states of NH3, populated by two-colour multiphoton excitation. The selected states, r anging from v(2)(+) = 0 to 7 and N+, K+ less than or equal to 4 are ac cessed via the B and C' states as intermediates. The application of mu ltichannel quantum defect theory to the understanding of the rotationa l propensities in the mass-analysed threshold ionization spectra is di scussed. It is demonstrated that the interactions of the Rydberg pseud o-continuum both with bound Rydberg states and with other continua can be modelled.