Leps potential energy surfaces for symmetrical alkali trimers

Abstract

Semi-empirical potential energy surfaces for M 3 (where M = Li through Cs) complexes are derived from the simplest form of the London approximation, by evaluating the Coulomb and exchange integrals as half of the sum and difference of two new interaction potential curves for the 1Σ + g and 3Σ + u states of M 2. For comparison the Morse and a modified an tiMorse potential have been included in the calculations. At small internuclear distances the potential surfaces show a shallow well which extends into the entrance and exit valleys without an energy barrier. The M 3 complexes attain maximum stability in the linear symmetric configuration; they remain almost equally stable, however, in the isosceles triangular configuration. The force constants corresponding to stretching and bending deformations of the trimers have been calculated for the linear configuration. It has been observed that unlike the stretching, the bending deformation does not sensitively affect the energy variation of the ground state of the trimers.