ИСТИНА

A comparison of laboratory and astronomical spectroscopic measurements could be used for discovery of the fundamental effects not described in the framework of the Standard Model. Due to a high sensitivity of the vibrational and rotational kinetic energies of molecules to nuclear masses, the high-redshift quasar absorption spectra of H2 and CO molecules are implied to probe a variation of the proton-to-electron mass ratio mp/me on a cosmological time scale [1] while a temporal variation of the fine structure constant α is normally investigated via measurements of the atomic lines shift. The recent unprecedented accurate spectroscopic measurement on the a3Π →X1Σ+ band of various CO isotopologues confirms the extreme sensitivity of electronic transitions involved nearly degenerate rovibronic levels for probing a variation of mass on a laboratory time scale [2]. The impact of relativistic interactions on the spectral characteristics of the ground X1Σ+ state of CO molecule was theoretically studied as well [3]. At the present work we estimated a sensitivity of the spin-forbidden triplet-singlet a3Π →X1Σ+ Cameron system of CO molecule onto a variation of the fine structure constant α since the pronounced impact of the α-value drifting on the spin-orbit splitting and relative intensity distribution into the intercombination transition should be expected. Therefore, both relativistic and mass effects could be treated simultaneously. The fully relativistic model of the electron system of the CO molecule was based on the Dirac-Coulomb-Gaunt approximation for the Hamiltonian which considered α as a variable parameter and used the “exact” transformation to the two-component picture. To describe the electron correlation we implied the large scale multi-reference configuration interaction (MRCI) method. To monitor of the MRCI energy convergence the various compositions of reference wave function and active space were employed. Potential energy curves of the excited states were obtained by adding the vertical excitation energies as functions of the internuclear distance to the accurate empirical ground state PEC [4]. The dependence of the fine structure rovibronic energies and transition dipole moments on the different values of the parameter α was studied in details. All calculations were accomplished by the DIRAC17 code [5]. The work was supported by the Russian Science Foundation; grant N 18-13-00269.