ИСТИНА

Among other alkali diatomics, the KRb molecule stands out, because of the high density of the low-lying electronic states, belonging to both singlet and triplet manifolds. This is attributed to the accidentaly close values of the ionization potential, electronic affinity and the polarizability of K and Rb atoms in their ground states as well as almost degenerate energies of the first excited 42P(K) and 52P(Rb) states. The high density of both covalence and ion pair states leads to a pronounced radial coupling effect between states with the same spatial and spin symmetry1. We performed the simplest two state diabatization of the mutually perturbed 11Π and 21Π states of KRb molecule by means of both ab initio electronic structure calculation and coupled-channel (CC) deperturbation treatment of the experimental spectroscopic data available for the (1~2)1Π complex2-4. The point-wise diabatic potential energy curves (PECs) of the interacting states and the relevant electronic coupled function were constructed by the simplest two state unitary transformation. The required transformation angle was determined by analytical integration of the radial coupling matrix element estimated by a finite-difference schema. Alternatively, the empirical PECs and electronic coupling function were obtained in the framework of the non-linear least squared fitting of both raw rovibronic3 and reduced vibronic2,4 experimental term values assigned to the (1~2)1Π complex. The deperturbation model based on an iterative solution of two close-coupled radial equations reproduces the experimental rovibrational term values of both 39K85Rb and 39K87Rb isotopologues3 with an accuracy of ~0.1 cm-1. Finally, the diabatization procedure has been used to transform ab initio spin-orbit and angular coupling matrix elements as well as the transition dipole moments into their diabatic counterparts. The resulting empirical PECs, combined with ab initio transformed electronic, spin-orbit, and angular coupling functions, are a good starting point for further overall deperturbation analysis of both singlet and triplet KRb states manifolds correlated with the second and third dissociation limits. The properly diabatizated (1~2)1Π-(X,A,C)1Σ+ transition dipole moments could be applied to radiative property estimates. We are deeply indebted to Claude Amiot for raw experimental data on the (1~2)1Π complex. The work was partly supported by the RFBR grant N 16-03-00529-a. References [1] T. Leininger, G.-H. Jeung, Phys. Rev. A, 51, 1929, 1995. [2] S. Kasahara, C. Fujiwara, N. Okada, H. Kato, M. Baba, J. Chem. Phys. 111, 8857, 1999. [3] C. Amiot, J. Verges, J. d’Incan, C. Effantin, Chem. Phys. Lett., 321, 21, 2000. [4] J.-T. Kim, Y. Lee, B. Kim, D. Wang, W. C. Stwalley, P. L. Gould, E. E. Eyler, Phys. Chem. Chem. Phys., 13, 18755, 2011.