Transition Properties Of Triplet And Singlet States Of Sulfur Monoxide Radicals

The potential energy function of molecules is of great significance for studying the structure and characteristics of molecules and substances.The process of valence electrons absorbing energy or releasing energy at one energy level to reach another energy level is called electronic transition.Among them,the molecular potential energy function is also used for the analysis of molecular spectral characteristics,allowing us to have a deeper understanding of diatomic molecules.Sulfur monoxide radical has important significance and role in astronomical and scientific research.From an astronomical perspective,this free radical was first discovered by a research team in the SgrB2 molecular cloud,and has been around for 20 years.Since then,research teams have observed this radical in supernovae,orbits of ring stars,translucent molecular clouds,and diffuse clouds.In previous research,some research groups have detected this SO radical in outer space.This suggests that this radical should be abundant in interstellar space.At the same time,the accurate transition characteristics between the different electronic states of the free radical are essential for astronomical observations.Because it is ubiquitous in the combustion reactions of sulfur-containing fuels,it has been receiving attention in spectroscopy and kinetics.In the past few decades,although a large number of theoretical studies have calculated the potential energy curve of the radical and the spectral constants of various electronic states,only a few theoretical studies have calculated the transition characteristics of the radical.At the same time,there are almost no experiments to measure the singlet state of the sulfur monoxide radicals,resulting in spontaneous vibration radiation.In order to make the molecular spectral characteristics and electronic transition characteristics of the radical more clear and perfect,we divide the work into two parts,namely the transition characteristics between the singlet state of the SO radical and the transition between the triplet state of the radical characteristic.This paper mainly studies the potential energy curves of SO radicals and the transition characteristics between different electronic states.Potential energy curves were calculated using the MOLPRO 2010.1 package in the C2v point group using the fully active space self-consistent field method(CASSCF),and then calculated using the icMRCI method and Davidson’s correction.First,the transition characteristics between several low-electron states of the triplet state of SO radicals are studied in this paper.These states are the X3∑-,A’3 △,A’’3∑+,A3Π,B3∑-,and C3Π states.These triplet states do not have double potential wells,only the C3 n state has a potential barrier,which is generated by avoiding the intersection with the 33 n state.In addition to discussing the spectral constants of these states,these A3 Π-X3 ∑-,B3 ∑--X3 ∑-,C3 Π-X3 ∑-,A3Π-A’’3 ∑+,C3 Π-A3Π,C3Π-A’’3 ∑+,B3∑A3 Π,C3 Π-A’3 △,and C3 Π-B3 ∑-,transition characteristics of transitions.Including Einstein coefficient A,transition probability,F-C(Franck-Condon)factor and radiant lifetime.Secondly,based on theoretical research,the transition characteristics between several low-electron states of the singlet state of SO radicals are calculated,namely a1△,b1∑+,c1∑-,d1Π,and e1Π states.We use the potential energy curves obtained by icMRCI+Q/56+CV+DK to obtain these states,fit their spectral constants De,Te,Re.ωe,ωexe,ωeye,Be,and αe,and calculate these using the LEVEL program Transition characteristics between states.Here De is the dissociation energy;Te is the excitation energy related to the ground state;Re is the equilibrium kernel distance;ωe is the resonance frequency;ω exe andω eye are the first-and second-order non-resonant dynamic constants;αe is the vibrational coupling constant;Be is the equilibrium Rotation constant.For the states of d1Π and e1Π,the distribution of the radiative lifetime as a function of the rotational quantum number at the same vibrational energy level is studied.Finally,comparing the spectral constant data and transition characteristics of these electronic states with previous experimental and theoretical research data,we can find that the triplet,singlet spectral constant,and transition characteristics of this paper are highly reliable and can be used in the future.Experiments and astronomical measurements provide theoretical references.