The rovibronic energies of the SiNSi radical in its X˜Πg2 electronic state

We present the results of a calculation of the rovibronic energies of the SiNSi radical in its X˜2Πg electronic ground state. At bent geometries, the electronic degeneracy is split to give a lower state of A2 symmetry and an upper state of B2 symmetry; each state is linear at equilibrium. The rovibronic calculation involves consideration of the Renner effect, and we initially made the calculation using ab initio A2 and B2 potential surfaces. The term values obtained were of help in making vibronic assignments in a newly obtained spectrum of the molecule. Having vibronically assigned the spectrum, we refined the potentials in a fitting to the vibronic term value separations. The optimized potentials allow us, in principle, to predict all rovibronic energies of the X˜Πg2 state.