The interplay of wave packet dephasing, optimization efficiency, and target state population in optimally controlled isotope selective photoionization

Abstract

The mutual dependencies of characteristic quantities for an isotope selective photoionization, namely optimization efficiency, target state population, and wave packet dephasing are presented for the NaK dimer. A pre-optimized pulse shape obtained from the maximization of the isotopomer ratio 23Na 39K/ 23Na 41K for the first excited electronic state serves as an initial guess for the subsequent optimization. For the ionization it provides almost vanishing population of the heavier ionic isotopomer and an ionic isotopomer ratio which is significant higher than the findings obtained from former investigations. The wave packet motions on the first excited state of the neutral molecule are in phase for both isotopomers. The optimization procedure, i.e. the simultaneous maximization of the 23Na 39K + photoionization yield and the minimization of the 23Na 41K + photoionization yield for the electronic ground state is based on optimal control theory and leads to a rise of ionic ground state population for both isotopomers related to a significant wave packet dephasing. Upon optimization the isotopomer ratio of the yields falls due to incidental resonances of vibronic transitions. The interplay of the observables are discussed and compared with the values obtained from an optimization which was started from a pure Gaussian pulse shape.