Peak D is thus also assigned to a vibronically allowed rather than FC allowed transition. This peak corresponds to an NO3 vibrational frequency of 1044 cm -1 , which could be either the 1 fundamental or the 3 fundamental proposed by Stanton. The intensity dependence of this peak supports its assignment to the vibronically allowed 1 0 3 transition rather than the FC allowed 1 0 1 transition, in agreement with Stanton's value for the 3 frequency. Moreover, the eKE-dependent photoelectron angular distributions for peaks B and D are similar to one another and differ considerably from that of peak A. Differing PADs across a photodetachment band are a well-known means of distinguishing FC allowed transitions from those allowed by vibronic coupling, and in this case offer further support for the assignment of peaks B and D to the latter type of transition.