Theoretical study of infrared and ultraviolet spectroscopy in SiP interstellar molecules

Abstract

ABSTRACT Insufficient theoretical investigation is being conducted on the spectroscopic characteristics within the infrared wavelength range of SiP, an identified interstellar molecule. Using the ic-MRCI method, potential energy functions and dipole moment functions for the ground state (${X^2}\Pi $) and low excited states (${{\rm{A}}^2}{\Sigma ^ + }$) of the SiP molecule were calculated. Based on experimental spectroscopy data, least squares fitting was used for the potential energy functions of the ${X^2}\Pi $ and ${{\rm{A}}^2}{\Sigma ^ + }$ states. By combining these potential energy and dipole moment functions, the one-dimensional Schrödinger equation was solved to obtain the vibronic energy levels and Einstein A coefficients for the electronic states. Partition functions of the SiP molecule from 0.1 to 3000 K and the radiative properties of ${X^2}\Pi \leftrightarrow {X^2}\Pi $ and ${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$ were derived. Infrared spectroscopy of the ${X^2}\Pi $ state and ultraviolet spectroscopy of the ${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$ transition at 100 K, a temperature crucial for astronomical research, were calculated. Results indicate that the spectral-line intensity of the ${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$ transition is greater, making it more suitable for astronomical observation. The obtained computational results in this paper yield spectroscopic parameters for the characterization of the interstellar molecule SiP, furnishing theoretical underpinnings for subsequent experimental observations.