Theoretical study on ultrafast chemical processes in terms of pump-probe photoelectron spectroscopy

点击翻译按钮获取中文摘要

We have developed a theory of energy- and angle-resolved photoelectron spectra for femtosecond pump-probe ionization of wavepackets and results of its application to the ^1Σ^+_μ double-minimum state of aligned Na_2. The formulation is well suited for inclusion of the underlying dynamics of molecular photoionization and its dependence on molecular geometry. Results have been obtained for three typical pump laser energies selected so as to investigate qualitatively different patterns of the spatio-temporal propagation of wavepackets on the double-minimum potential curve and of their associated photoelectron spectra. Photoelectron angular distributions have been given for different orientations of linearly polarized pump and probe pulses. The resulting photoelectron spectra illustrate the importance of a proper description of the underlying photoionization amplitudes and their dependence on geometry for unravelling wavepacket dynamics from pump-probe photoelectron signals in non-adiabatic regions where the electronic structure evolves rapidly with geometry. The present theory was extended so as to treat a system of nonadiabatic transition such as that in NaI molecule, whose ground and first excited potential curves intersect with each other due to intramolecular electron transfer. It has been shown for the first time that the bifurcation of nuclear wavepackets can be directly and experimentally observed with the pump-probe photoelectron spectroscopy. This is of great importance both in chemistry, wave-pacekt engineering, quantum chaos, the fundamental quantum theory, and so on.