A THEORETICAL STUDY OF THE A 2&'¨X 2% SYSTEM OF THE SiP MOLECULE1

The A 2&' and X 2% electronic states of the SiP species have been investigated theoretically at a very high level of correlation treatment (CASSCF/MRSDCI). Very accurate potential energy curves are presented for both states, as well as the associated spectroscopic constants as derived from the vib-rotational energy levels determined by means of the numerical solution of the radial Schroe dinger equation. Electronic transition moment function, oscillator strengths, Einstein coefficients for sponta- neous emission, and Franck-Condon factors for the A 2&'¨X 2% system have been calculated. Dipole moment functions and radiative lifetimes for both states have also been determined. Spin-orbit coupling constants are also reported. The radiative lifetimes for the A 2&' state, taking into account the spin-orbit diagonal correction to the X 2% state, decrease from a value of 138 ms at v@ \ 0 to 0.48 ms at v@ \ 8, and, for the X 2% state, from 2.32 s at v@@ \ 1t o 0.59 sa tv@@ \ 5. Vibrational and rotational transitions are expected to be relatively strong. Subject headings: ISM: moleculesmolecular datamolecular processes