A THEORETICAL CHARACTERIZATION OF THE QUARTET STATES OF THE SO+ MOLECULAR ION

The quartet states of the SO+ molecular ion are described theoreticall y using the internally contracted multireference configuration interac tion approach and natural orbitals generated from a state-averaged den sity matrix. Correlation-consistent polarized-valence quadruple-zeta a tomic functions are used in the expansion of the one-electron basis. P otential energy curves are presented for all the states, and solutions of the radial Schrodinger equation allowed the determination of vibra tional energy differences and spectroscopic constants. For the b (4)Si gma- state, this study corroborates the available experimental data an d extends the spectroscopic information to regions not yet accessed ex perimentally; an alternative explanation for the predissociation mecha nism is also suggested, For the a (II)-I-4 state, our data and analysi s are indicative that the vibrational spectroscopic constants derived from the photoelectron spectra might be underestimated. It also leaves open the possibility that the experimental vibrational level numberin g might have to be increased by one unit. Transition probabilities as given by the Einstein A coefficients, and Franck-Condon factors are al so provided to help analyze the experimental data. Of immediate releva nce to the direct ion-fragment spectroscopy, this study predicts the e xistence of a new bound (II)-I-4 state in the energy range of photons used in these experiments. This new state crosses the b (4)Sigma(-) cu rve very close to where it was supposed to be crossed by the 1 (4)Sigm a(+), and its repulsive side runs almost parallel to this latter state . Our theoretical prediction places the 1 (4)Sigma(+) State still lowe r than it was inferred experimentally. For the a (II)-I-4-1 (4)Sigma() transition we have also computed the transition moment function and showed that its constancy assumed in the simulation of the experimenta l intensity data is not valid. (C) 1998 American Institute of Physics.