Ab initio potential energy curves of Rydberg, valence and continuum states of NO

Bound states and quasibound Rydberg states of NO are studied as a function of internuclear distances in the range 1.6-3.024 a(0). R-matrix calculations which include 12 configuration interaction target states in the close-coupling expansion are performed. Rydberg states of up to n = 10 are studied for the (2) Sigma(+), (2) Pi and (2) Delta symmetries of NO. Intruder states, of both valence and Rydberg character, are followed both above and below the ionization threshold. Where possible these states are classified as Rydberg states of an excited state of the ion. Away from avoided crossings, it is found that the quantum defects of the Rydberg series converging on the X (1) Sigma(+) state of NO+ show little sensitivity to bondlength but show considerable dependence on the number of states included in the close-coupled expansion.