Measuring the predissociation and rotational autoionization of the vibrationless Rydberg series in ammonia

A novel method is presented to retrieve the average predissociation rate an d the average rotational autoionization rate of a molecule by measuring the field ionization spectrum only, Both an intuitive picture and a quantitati ve description are derived for the competition between the three decay chan nels. field ionization. rotational autoionization, and predissociation. Fie ld ionization spectra of various rotational states of ammonia are presented and fitted. From the fits we found that the average predissociation rate o f the Rydberg series converging to the vibrationless N+ = 3 ionic state is about equal to the average rotational autoionization rate to the Rydberg se ries converging to the vibrationless N+ = 2 ionic state. namely 1 x 10(15)/ n(3) s(-1). (C) 2001 American Institute of Physics.