THE SPLITTING OF EXCITED ELECTRONIC STATES IN OPTICALLY INACTIVE MOLECULES DUE TO THE PARITY-VIOLATING ELECTRON-NUCLEAR INTERACTION

This paper considers optically inactive molecules possessing a symmetr y plane. Degenerated excited electronic states in such molecules may, in principle, differ in symmetry with respect to mapping onto the symm etry plane. Should this prove the case, the parity-nonconserving elect ron-nuclear interaction (PNI) causes the degenerated electronic level to suffer a splitting linear in the Weinberg constant. The paper analy zes from this standpoint the lowest-lying excited states in the ten-el ectron HF, NH3, B-2, and H2O molecules. Two of them, namely HF and NH3 , possess the necessary and sufficient symmetry properties for such a linear splitting to occur. Factors are discussed that augment the PNI- induced splitting of the excited states under consideration in compari son with the splitting of the ground state in left- and right-handed m odifications of optically active molecules. Computations confirm the o ccurrence of a great (approximate to 10(-13) eV) splitting of the leve ls being considered due to the PNI effect. A similar effect can also o ccur in the electronic ground state of paramagnetic molecules, such as NO. The computation uses the consistent multiple-electron perturbatio n theory with a model single-electron central field bare potential. Th e computer code used is a modification of the original code developed for precision atomic calculations. All the computations boil down to t he solution of a single set of ordinary differential equations, i.e., a unidimensional procedure. (C) 1997 American Institute of Physics.