Theoretical investigation of electronic states and spectroscopic properties of tellurium selenide molecule employing relativistic effective core potentials

• Selection of basis sets and relativistic effective core potentials (RECP) of Te and Se atoms.
• Computation of MRDCI calculations without and with considering effect of spin–orbit coupling.
• Construction of potential energy curves without and with spin–orbit effect.
• Computation of spectroscopic constants without and with spin–orbit effect.
• Computation of transition probabilities of some transitions and dipole moments.

Ab initio based relativistic configuration interaction calculations have been performed to study the electronic states and spectroscopic properties of tellurium selenide (TeSe) – the heaviest heteronuclear diatomic group 16–16 molecule. Potential energy curves of several spin-excluded (Λ–S) electronic states of TeSe have been constructed and spectroscopic constants of low-lying bound Λ–S states within 3.85 eV are reported in the first stage of calculations. The X3Σ−, a1Δ and b1Σ+ are found as the ground, first excited and second excited state, respectively, at the Λ–S level and all these three states are mainly dominated by …π4π*2 configuration. The computed ground state dissociation energy is in very good agreement with the experimental results. In the next stage of calculations, effects of spin–orbit coupling on the potential energy curves and spectroscopic properties of the species are investigated in details and compared with the existing experimental results. After inclusion of spin–orbit coupling the X13Σ0+- is found as the ground-state spin component of TeSe. The computed spin–orbit splitting between two components of X3Σ− state is 1285 cm−1. Also, significant amount of spin–orbit splitting are found between spin–orbit components (Ω-components) of several other excited states. Transition moments of some important spin-allowed and spin-forbidden transitions are calculated from configuration interaction wave functions. The spin-allowed transition B3Σ−–X3Σ− and spin-forbidden transition b1Σ0++–X13Σ0+- are found to be the strongest in their respective categories. Electric dipole moments of all the bound Λ–S states along with those of the two Ω-components of X3Σ− are also calculated in the present study.

Potential energy curves of low-lying bound Λ–S states of TeSe.Figure optionsDownload as PowerPoint slide