Radiative properties of low-lying triplet states of the NaK molecule

The electric dipole moment functions for transitions between low-lying trip let states of the NaK molecule are calculated by the finite-field method in conjunction with the many-body perturbation theory using multiple partitio nings of the total Hamiltonian. On the basis of these functions of the tran sition dipole moments and empirical Rydberg-Klein-Rees potentials of combin ing electronic states, the radiative lifetimes of vibrational levels of the b(3)Pi, c(3)Sigma(+), and d(3)Pi states are estimated. The influence of th e spin-orbit interaction between singlet and triplet states on the effectiv e lifetimes of perturbed vibrational levels of the singlet-triplet complexe s is discussed.