ИСТИНА

The thesis presents experimental and energy-based deperturbation analysis of the strongly mixed singlet and triplet electronic states in the Rb2 (A1Sigma+_u ~ b3Pi_u), NaCs (A1Sigma+ ~ b3Pi) and NaK (D1Pi ~ d3Pi) molecules. The Doppler-limited rovibronic term values of the singlet-triplet A~b and D~d complex were obtained from analysis of collisionally enhanced laser induced fluorescence spectra to the ground X-state, which were measured by Fourier Transfer Spectrometer at an instrumental resolution of 0.03-0.08 cm-1. In addition to direct laser excitation of the levels of the complex, one- and two-colour double resonance excitations scheme are used as well. The coupled-channel approach was adopted to deperturb the singlet-triplet complexes above. The Hamiltonian constructed in Hund’s case (a) basis functions accounts explicitly direct spin-orbit coupling between the singlet and triplet states, spin-orbit splitting effect in the triplet state, and spin-rotational coupling between Omega = 0,1,2 components of the triplet. The indirect interactions caused by regular perturbations with remote electronic states also were taken into account in the framework of Van Vleck contact transformation. Analytical mapping procedure, based on a reduced variable representation of the radial coordinate, was combined with difference approach to limit in order to improve the computational efficiency for the uniform finite-difference grid solution of the coupled-channel equations. The deperturbation models reproduce the input experimental data set with a standard deviation closed to the uncertainty of measurements of about 0.003-0.05 cm-1. Reliability of the deperturbed parameters also is confirmed by a good agreement of the predicted term values of different isotopologues as well as relative intensity distribution simulated into relevant LIF spectra. The resulting parameters of the NaCs A~b complex were used to calculate transition probabilities of the two-step optical cycle for ultracold NaCs molecule production.