Configuration Interaction Study On Excited Electronic States Of The SrH Molecule

Strontium monohydride(SrH)is one category of the alkaline-earth metal hydrides,which is playing an important role in many filed within astrophysics,chemical engineering and hydrogen storage.Therefore,spectroscopy of SrH molecule has important practical value and theoretical significance.In our work,the electronic states structures,spectrum information and transition properties of SrH molecule are calculated by using the internally constriction multi-reference configuration interaction(ic MRCI)method and the Davidson correction(+Q).The main contents are as follows:(1)High-level ab initio calculations on 16 ?-S electronic states of five dissociation limits(Sr(1Sg)+H(~2Sg),Sr(3Pg)+H(~2Sg),Sr(~3Dg)+H(~2Sg),Sr(~1Dg)+H(~2Sg)and Sr(~1Pu)+H(~2Sg))of the SrH molecule have been carried out utilizing the ic MRCI+Q method,with small-core relativistic effective core potentials together with the corresponding correlation consistent polarized valence basis sets.The size-consistency error is balanced by the Davidson(+Q)correction.The potential energy curves(PECs)of the 16 ?-S states have been obtained with the aid of the avoided crossing rule between electronic states of the same symmetry.It is found that 10 of the 16 calculated excited states correspond to bound states.Furthermore,the spectroscopic constants of the bound states were calculated,most of which have been reported for the first time,with those pertaining to the X~2?~+,A~2?,B~2?~+,and A'~2? states being in line with the available experimental and theoretical values.The permanent dipole moments(PDMs)of the bound states are calculated.All the calculated PDMs tend to zero at large distance,confirming that the dissociation products are both neutral atoms.The PDM of the F~2?~+ state tends to zero at a slower speed,through by analyzing the electronic configuration component,we can sure that the F~2?~+ state is a Rydberg state.(2)We used the finite difference calculation to compute the wave functions,obtained by Multiconfiguration Self-consistent Field(MCSCF)method,to acquire the non-adiabatic matrix elements(including the radical coupling matrix element and rotational coupling matrix element).Then we achieved the changing of the non-adiabatic matrix elements with the internuclear distance.The coupling matrix elements lead to the asymptotic limit close to 1a.u,when two states correspond to the same dissociation limit.If that correspond to the different dissociation limits,the asymptotic limit is closed to 0a.u.(3)Due to SrH having a high density of states in the Franck-Condon region strong interactions,e.g.via spin-orbit coupling(SOC),exist between the adjacent states.The interaction strength between the ?-S states,which are in the high density region of electronic states,are studied via the magnitude of spin-orbit matrix element.The SOC splits the lowest strongly bound X~2?~+,A`2?,A'~2?,E~2?,B~2?·+ and D~2?~+states into 9 ? states.Then,the spectroscopic constants of the ? states were calculated.(4)The transition properties of the bound ?-S states were predicated,including the transition dipole moments(TDMs),the Franck-Condon factors(FCFs),and the spontaneous radiative lifetimes.The calculated results of radiative lifetimes are in accordance with the experimental values.The lifetimes were calculated to be 34.2ns(?'=0)and 55.0ns(?'=0)for A~2? and B~2?~+,in good agreement with the experimental results of 33.8±1.9ns and 48.4±2.0ns.