  In high orbital angular momentum ($\ell \geq 3$) Rydberg states, the
centrifugal barrier hinders close approach of the Rydberg electron to the
ion-core. As a result, these core-nonpenetrating Rydberg states can be well
described by a simplified model in which the Rydberg electron is only weakly
perturbed by the long-range electric properties (i.e., multipole moments and
polarizabilities) of the ion-core. We have used a long-range model to describe
the vibrational autoionization dynamics of high-$\ell$ Rydberg states of nitric
oxide (NO). In particular, our model explains the extensive angular momentum
exchange between the ion-core and Rydberg electron that had been previously
observed in vibrational autoionization of $f$ ($\ell=3$) Rydberg states. These
results shed light on a long-standing mechanistic question around these
previous observations, and support a direct, vibrational mechanism of
autoionization over an indirect, predissociation-mediated mechanism. In
addition, our model correctly predicts newly measured total decay rates of $g$
($\ell=4$) Rydberg states because, for $\ell\geq4$, the non-radiative decay is
dominated by autoionization rather than predissociation. We examine the
predicted NO$^+$ ion rotational state distributions generated by vibrational
autoionization of $g$ states and discuss applications of our model to achieve
quantum state selection in the production of molecular ions.
