%0 Generic
%A Chiang, Ying-Chih
%D 2012
%F heidok:14017
%R 10.11588/heidok.00014017
%T Nuclear Dynamics in Electronic Decay Processes followed by Fragmentation
%U https://archiv.ub.uni-heidelberg.de/volltextserver/14017/
%X The impact of the nuclear dynamics during an electronic decay process  followed by fragmentation in a diatomic system is investigated for three  different examples, by using a time-dependent approach.    The first example is the prediction of the interatomic Coulombic decay  (ICD) process in NeAr, following the Ne 1s Auger decay. It is a two-step  (cascade) decay process where the first step is a fast Auger decay and the  second step is the ICD of interest. A full cascade calculation has been  performed to provide the (time-resolved) Auger electron and (time-resolved)  ICD electron spectra. Our results show that the line width of the Auger  electron spectrum contains also the information on the total ICD width at  the equilibrium internuclear distance of NeAr. In addition, simulations show  that the nuclear motion during the first Auger step has no impact on the  following ICD process.  This ICD process has been verified by experiment,  and if a simple modification of the ab initio ICD transition rate is adopted,  our simulated ICD spectrum agrees well with the experimental result.    For an electronic decay process followed by fragmentation, the energy  spectrum of the emitted electron and the kinetic energy release (KER)  spectrum of the ionic fragments are usually considered to be mirror images  of each other. This is termed "mirror image principle" and is often applied  in experiments. It is usually valid for the ICD electron spectrum and its  corresponding KER spectrum. However, the principle is merely an empirical  rule and can break down even in a diatomic system. The molecular Auger  process in CO is chosen as the second example, as it exhibits such a break  down of the mirror image principle. Calculated KER and electron spectra  for this process also agree well with experiment.    The resonant Auger process of HCl is chosen as the last example to  demonstrate that the interaction between a molecule and an intense laser  pulse (as are available today in free electron lasers) can lead to a  strong light-induced non-adiabatic effect. It is a general effect that  can be found in molecules interacting with an intense laser pulse, which  gives rise to strong molecular overall rotation.    Besides the above applications, a new elegant and numerically efficient  formulation for evaluating the (time-resolved) KER spectrum in an electronic  decay process followed by fragmentation is derived in this work. The KER  spectrum now has a simple physical interpretation: it is the accumulated  (over time) generalized Franck-Condon factor between the nuclear wave  packet on the intermediate decaying state and the discrete continuum  eigenfunctions of the dissociative final state. This new representation  allows one to analyze the KER and the electron spectra, and it provides  the conditions for the mirror image principle to hold.