| Diatomic molecules(radical or cation)containing Br,Be,Si,C and N play an important role in many fields,such as physical applications and chemical production.For example,the free radical bromide oxide(BrO)plays an important role in the catalytic reaction of stratospheric ozone.Beryllium boride(BeB)is a relatively stable radical,which is widely used in beryllium alloy manufacturing and nuclear industry that due to its low density,high hardness and high sound velocity.Chemical elements such as carbon,phosphorus and silicon are abundant around stars.Since CP+ cation are likely to exist large quantities in stars,atmosphere and interstellar space.Study on spectroscopic properties of CP+ cation has become a research hotspot of astrophysics in recent years.Part of the current astrophysics has been studied about SiC radical,and of course it is expected that SiC+ cation will also be observed in interstellar space.As a kind of astral molecule,NS radical has been confirmed in the early interplanetary space research.However,it was not until 2018 that NS+ cation was observed as a kind of stellar molecule which by studying the spectra of cold molecular clouds,stellar prenuclei and shock waves.Therefore,the systematic study of the electronic structure and spectroscopy for Br,Be,Si,C,N diatomic molecules is not only of great theoretical value,but also of great application value in industrial production,interstellar exploration and other fields.In this paper,BrO and BeB radicals,as well as CP+,SiC+ and NS+ cations are studied which are mainly focuse on spectroscopic properties(potential energy curve,spectroscopic constant,vibration level)and transition characteristics(Franck-Condon factor,Einstein coefficient,radiation lifetime).First,using the complete active space self-consistent field method,which is followed by the valence internally contracted multireference configuration interaction to calculate the potential energy curves for 12Λ-S state of BrO radical,16 Λ-S state of BeB radical,18 Λ-S state of CP+ cation,12 Λ-S stats of SiC+cation,8 Λ-S state of NS+ cation.To improve the quality of potential energy curves,core-valence correlation and scalar relativistic corrections as well as the extrapolation to the complete basis set limit are taken into account.Based on the calculated PECs,we get corresponding Λ-S bound state of spectroscopic constant and vibration level,including equilibrium internuclear distance Re,dissociation energy De,excitation energy Te,resonance frequency ωe,first and second order inharmonic constants ωexe and ωeye,equilibrium rotational constant Be,vibrational coupling constant ae,and the calculated spectroscopic constant are compared with experimental and theoretical data in the literature.In addition,the spin-orbit coupling effects on spectroscopic constant and vibrational energy levels of these diatomic molecules are also investigated.Calculation method is based on the Davidson correction,which is followed by icMRCI+Q theory and breit-pauli coupling operator.In this paper,we calculate potential energy curve of selected 4 Ω state for BrO radical,36 Ω state of BeB radical,50 Ω state of CP+cation and 27 Ω state of SiC+ cation,that the spin-orbit coupling effect on spectroscopic constant is predicted.For the BrO radical,the calculated results show that the 24Π state was repulsive state;A2Π state has one barrier;12Δ,12Σ+,12Σ-,22Σ-,24Σ-,14Σ+,14Δ and 14Π states are weakly bound;the avoided crossings existed between the A2Π and 32Π states;the X2Π,A2Π,14Δ,14Π,and 24Π states were inverted with the SOC effect taken into account For the BeB radical,the calculation results show that d4Δ,e4Σ+,g4Π,24Σ+and I2Σ+ states have double wells,but the d4Δ,e4Σ+,and g4Π states as well as the second well of the h4Π state are determined to be very weakly bound;the G2Π,b4Π,and g4Π states are inverted with the SOC effect accounted for.For the CP+cation,the results show that the 25Π state is repulsive;the 13Σ+,15Σ+,15Σ-,and 15A states have a double well;the 25Σ+state has a single well and a barrier;the 13Σ+,23Σ+,and 15Σ+states were inverted when the SOC effect was accounted for.For the SiC+cation,all the 12 Λ-S states are bound;b2Π,14Π,24Π and 24Σ-states have one barrier;b2Π and 14Π states have double wells;the avoided crossings existed between the 14Π and 24Π states.For the NS+ cation,no repulsive quintet states exist;no quintet states have barriers,and no quintet states possess a double well;the 15A and 25A states are very weakly bound;there are many crossing between these PECsSecond,we use icMRCI+Q method with LEVEL program to calculate the transition of diatomic molecules between A-S state,which is based on potential energy curve.Among them,we study transition characteristics of X2Π-A2Π,12Δ-12Σ-,14Π-14Σ+,12Σ--22Σ-,A2Π-12Δ and 14Δ-a4Σ-for BrO radical;the transition characteristics of A2Σ+-X2Π,B2Π-X2Π,B2Π-A2Σ+,C2Δ-X2Π,C2Δ-B2Π,D2Σ-X2Π,D2Σ--B2Π,E2Σ+-X2Π,E2Σ+-A2Σ+,E2Σ+-B2Π,G2Π-X2Π,I2Σ+-X2Π,G2Π-B2Π,G2Π-A2Σ+and G2Π-C2Δfor BeB radical;the emissions for the 23Π-X3Π,23Π-13Σ-,23Σ+-23Π,23Σ+-X3Π,13Σ+-X3Π,23Π-13Σ+,13Δ-x3Π,13E--X3Π,23Σ+-13σ+,21Π-11Π,11Δ-11Π,21Π-21Σ+,21Π-11Σ-,11Σ-11Π,21Π-11Δ,21Σ+-11Π,25Σ+-15Π,13Δ-23Π,15Σ+-15Π,21Π-11∑+,15Δ-15Π,15Σ-15Π,21Σ+-11Σ+,11Π-11Σ+and 25Σ+-15E+systems of CP+cation;the emissions for the 22E--e2II,24Σ--14Π,e2Π-d2Σ+,24Σ--X4Σ-,22Π-a2Δ,e2Π-c2Σ-,22Σ--c2Σ-,14Π-14Σ+,14Π-X4Σ-,14Π-A4Δ,24Π-A4Δ,24Π-14Σ+,24Π-14Π,24Π-24Σ-and 24Π-X4Σ-systems of SiC+cation;the emissions for the 35Σ+-15Π,25Δ-25Π,35E+-25II,25Δ-15II,25Δ-15Δ,35Σ+-25Σ+,35Σ+-15Σ+,25Σ+-15Π,15Δ-15Π,25Π-15Σ+,25Π-25Σ+,25Π-15Δ,25Σ+-15Σ+,15Π-15Σ+and 25Π-15Π systems of NS+cation.Band origins,Franck-Condon factors and Einstein coefficients of all spontaneous emissions are calculated comprehensively.Their spontaneous emission lifetime is calculated and the observable region of these electronic states is predicted.For the SiC+and NS+cation,the vibrational band origins and spectral range of the spontaneous emissions are evaluated for each transition system.In detail,for the SiC+ cation,the rotationless radiative lifetimes of vibrational levels are approximately 10-7 s for the 24Π and 24Σ-states,10-5 to 10-6 s for the 22Σ-state and the first well of 14Πstate,10-5 s for the e2Π state,and very short for the second well of the 14Π state;the Einstein coefficients of many emissions are large between the 22Σ-and the c2Σ-state,the e2Π and the a2Δ state,the 24Σ-and the X4Σ-state,the 24Π and the X4Σ-state,the first well of the 14II state and the X4Σ-state,as well as the second well of the 14II state and the 14Σ+state.In combination with the radiative lifetimes,we confirm that these emissions should be not difficult to detect.For the NS+ cation,the rotationless radiative lifetimes of the vibrational levels are approximately 10-5 to 10-6 s for the 25Σ+ state,10-5 s for the 15II state,and 10-4 to 10-5 s for the 35Σ+ and 25Π states,the rotationless radiative lifetimes of the vibrational levels are very long for the spontaneous emissions generating from the 15Δ and 25Δ states;the spectral range of the 25Σ+-15Σ+system extends from the visible region to the near-infrared region,most of the strong emissions are of visible light,and only a few are in the near-infrared region;for the 25Π-15Σ+system,all emissions fall into the visible region;for the 25Π-15Π system,the spectral range extends from the visible region to the infrared region;the strong emissions are in the near-infrared region;for the 25Π-25Σ+ system,the spectral range is in the infrared region.For the 35Σ+-15Σ+system,the spectra fall mainly into the visible and near-UV regions,the strong emissions are in the visible region;for the 35Σ+-15Π system,the spectral range extends from the visible region to the infrared region,the most intense emissions from this system are in the infrared region.In conclusion,the spectroscopic constants of Ω state and transition properties of most transition bands are reported for the first time.Spectroscopic parameters,vibrational levels,and transition probabilities obtained in this paper can be considered very reliable and employed as helpful guidelines for studying spectroscopy experiment in near future. |
