Spectroscopic Property Research Of The Low Excited States Of HeH Radical

Hydrogen and helium are the earliest two elements that emerged in the universe,which play a significant role in exploring the evolution of the universe and the origin of elements.Hydrogenated helium diatomic molecule can produce the cooling effect since it has strong dipole moment characteristics and Rydberg structure.Therefore,it can be the main candidate molecule in the study of the primordial gas coolant in the universe.In the present work,spectral properties of the four lowest electronic states（X²Σ⁺,A²Σ⁺,B²Πand C²Σ⁺）corresponding to the dissociation limits（H（1s）+He（1s²）,H（2s）+He（1s²）and H（2p）+He（1s²））of the HeH radical are calculated by performing high-precision ab initio calculations.A series of spectral characteristics such as potential energy curves,spectral constants,spin-orbit coupling,predissociation lifetimes and radiation lifetimes are obtained based on the theoretical calculation.The main research contents are as follows:1.Potential energies of the four electronic states of X²Σ⁺,A²Σ⁺,B²Πand C²Σ⁺are calculated using the internally contracted multireference configuration interaction（ic-MRCI）method based on the correlated consistent basis set of aug-cc-p V6Z in the internuclear distance range of 0.4-8?.To improve the computational accuracy of potential energy curves,additional Rydberg basis functions and the Pople correction are used to optimize the calculations.Equilibrium internuclear distance R_e,harmonic vibrational frequencyω_e,first anharmonic termω_eχ_e,equilibrium rotational constant B_e,vibration–rotation coupling constantα_e,dissociation energy D_e,zero-point energy D₀,centrifugal distortion constant D and rotational constantβ_e of the excited states are obtained by fitting the ro-vibrational levels of the excited electronic states.By comparison,newly computed spectroscopic results are found to be consistent with the corresponding experimental data and more accurate than the literature theoretical values.2.The spin-orbit coupling effect of the B²Πstate is calculated using the Breit-Pauli operator,and the splitting of potential energies is analyzed.The predissociation mechanism of the C²Σ⁺state is studied based on the Heisenberg uncertainty principle since the energy barrier of the potential energies curve and the predissociation lifetimes of C²Σ⁺are calculated.The lifetimes ofυ=0–5/N=0for A²Σ⁺and C²Σ⁺andυ=0–5/N=1 for B²Πare also calculated based on the Fermi Golden role and elaborated in detail.3.Emission spectral properties of electronic states are studied according to the ab initio method.Transition dipole moments varying with the internuclear distance corresponding to the transitions A²Σ⁺-X²Σ⁺,B²Π-X²Σ⁺,C²Σ⁺-X²Σ⁺,B²Π-A²Σ⁺,C²Σ⁺-A²Σ⁺and C²Σ⁺-B²Πare also derived to research the transition properties.Based on the potential energies and transition dipole moments,Einstein coefficients A of those transitions are obtained.Subsequently,the radiation lifetimes and emission spectra of the first eight vibrational energy levelsυ=0–7 are calculated,including the bound-continuum and bound-bound systems.Furthermore,the emission spectra for the bound-continuum and bound-bound systems at different temperatures are simulated,and the particle number populations are calculated at different temperatures to research the effect of the temperature.