COMPETITION BETWEEN EXCITATION AND ELECTRONIC DECAY OF SHORT-LIVED MOLECULAR-STATES

The nuclear dynamics accompanying the excitation to and the subsequent decay of an electronic state is discussed. Particular attention is pa id to cases, in which the whole process cannot be divided into two ste ps (excitation and decay) since the excitation and the decay times are of the same order of magnitude. The recently introduced time-dependen t formulation of the theory describing the wave packets' dynamics is e xtended to include the excitation process. The wave packets can be rel ated to the intensity of the emitted particles. Most of the resulting integrals can actually be performed by employing eigenstates of the Ha miltonians corresponding to the involved potential energy surfaces. Th is leads to the so called ''time-independent'' formulation of the theo ry. Computational details of the implementation of the corresponding ' 'time-dependent'' and ''time-independent'' methods are presented. Illu strative applications are given to illuminate both the influence of th e excitation process and the lifetime of the decaying state. It emerge s that the intuitive interpretation of the spectra (within the above t wo step model) may fail. Insight into the process is gained by studyin g the evolution of the spectra as a function of time. The appearance o f ''atomic lines'' due to dissociative decaying and final states is in vestigated in some detail.