Singlet-triplet interaction of the adiabatic terms X~1Σ+ and a~3Σ+ in the linear triatomic molecules

• Published in: Chemical physics letters 2021-07, Vol.775, p.138620, Article 138620
• Main Authors: Volokhov, V.M., Poluyanov, L.V.
• Format: Article
• Language: English
• Subjects: Molecular symmetry group; Space-matrix symmetry operators; Spin-orbital coupling; Taylor series expansion for electronic Hamiltonian; Vibronic matrix; Vibronic symmetry operators
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2021.138620

[Display omitted] •We obtained all elements of symmetry group (spin-orbital interaction is accounted).•Vibronic symmetry operators and time reversal operator are constructed.•Vibronic matrix 4 × 4 of relativistic pseudo effect of Renner is deduced.•Potential energy surfaces are analyzed. The paper introduces the 4x4 vibronic matrix that describes singlet–triplet interaction of adiabatic terms 1Σ+ and 3Σ+ via deformation π-modes of the linear triatomic system. Our analysis takes into account spin-orbital coupling in ab initio Breit-Pauli form in the framework of two-electronic model. It is shown that the symmetry operators of electronic Hamiltonian include both space operations (acting on electronic coordinates) and matrix operations (acting on electronic spins). Eigenvalues of vibronic matrix (i.e. potential energy surfaces) are invariants of the molecular symmetry group C∞ν. The 4x4 vibronic matrix includes 4 electrostatic parameters and 3 parameters caused by spin-orbital interaction.