Theoretical electronic structure with rovibrational and dipole moment calculation of SiN Molecule

Abstract

Atomic and molecular data are at the origin of the atmospheres of planetary and stellar objects discoveries. Based on the laboratory astrophysics and the computational molecular spectroscopy, the interpretation of this data can give the chemical compositions and temperatures of these astrophysical systems. The detection and the identification of the SiN radical in the interstellar medium has drawn the attention to the gas phase chemistry and the evidence of a link between the interstellar chemistry of silicon and that of nitrogen. The quantum chemistry methods used to predict the spectroscopic properties of the SiN molecule can be calibrated with some available experimental results. In order to obtain reliable theoretical data that may help in the interpretation of interstellar or laboratory spectra concerning the SiN molecule, we performed theoretical calculation of 31 low-lying electronic state, below 66000 cm−1, of the molecule SiN by using the Complete Active Space Self Consistent Field (CASSCF) method followed by the Multi Reference Configuration Interaction with Davidson correction MRCI+Q. The potential energy along with the dipole moment curves of these states have been calculated along with the spectroscopic constants Re, ωe, Be, and Te. The Rotation-vibration lines for the considered electronic states of SiN molecule were obtained by direct solution of the nuclear motion Schrödinger equation using the canonical approach with program Rovib-1. By comparing our investigated values of the calculated vibrational energy Ev, the rotational constant Bv and the turning points Rmin and Rmax. with those available in literature shows a very good agreement. To the best of our knowledge nine new electronic states have been studied here for the first time that have not been observed yet.