Photoassociation Spectroscopy: Determination of Parameters of Potentials of Diatomic Molecules

Laser-induced fluorescence studied with the help of a tunable dye laser is used to record the photoassociation spectrum of equilibrium mercury atoms in the range of 34 700–37 300 cm–1. The so-called Franck-Condon structure, which represents periodic variations of absorption intensity on a continuous background, is observed. The structure makes it possible to determine spectroscopic parameters of the upper bound potential and the lower repulsive potential, including the potential with a shallow Van der Waals well. The Numerov-Cooley procedure is used to find the numerical solution of the boundary problem, namely, eigenfunctions and eigenvalues of the Schrödinger equation for the one-dimensional motion in a potential field, matrix elements of transitions and partial waves, and the absorption spectrum of collisional pairs of atoms are calculated. The absorption spectrum of mercury dimers was simulated taking into account 100 vibrational and 200 rotational levels. The comparison of theoretical and experimental spectra according to Tellinghuisen made it possible to determine the lower part of the potential curve for the dimer excited state.