Potential energy curves of low-lying states of the CN molecule taking into account relativistic and quantum-electrodynamic corrections

By the method of multireference configuration-interaction in the basis of Dirac–Fock–Sturm orbitals, a relativistic first-principles calculation of the potential energy curves of low-lying $X^2\Sigma^+_{1/2}$ and $A^2\Pi_{1/2}$ states of the CN molecule in the range of internuclear distances 0.8–8.0$\mathring{\mathrm{A}}$ has been performed. Using the method of the model Lamb shift operator, quantum-electrodynamic corrections to the total energy of the molecule for the given states have also been calculated. The contribution of quantum-electrodynamic corrections to the equilibrium internuclear distance $R_{AB}^e$, dissociation energy $D_e$, and vibrational constant $\omega_e$ of the ground state of the CN molecule is considered.