SELECTIVE MODE EXCITATIONS IN THE ELECTRONIC GROUND-STATES OF H2O, HDO, SIH2, AND NH2

Based on ab initio three-dimensional functions of potential energy, electric dipole and transition moments, the rovibronic energy levels, eigenfunctions, and radiative transition probabilities have been calculated for several triatomic molecules (H2O, HDO, SiH2, and the Renner-Teller system of NH2). Using ultrashort infrared picosecond laser pulses;the state-selective multiphoton excitations of the v1 = 4 (symmetric stretching) vibrational eigenstate of these molecules as well as the corresponding diatomics OH, SiH, and NH have been investigated. The OH stretching mode in HDO and in H2O can be selectively populated. Strong anharmonic coupling (SiH2) or Renner-Teller coupling to another electronic state (NH2) may, however, considerably reduce the achievable state selectivity.