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要旨:
In this
thesis, the results of the strong-field photoionization of various gas targets, particularly
of methane are presented. The photoionization was performed by focusing an ultrashort
two-color laser pulse into the supersonic gas jet of a Reaction Microscope. The capability
of the Reaction Microscope of simultaneous detection and identification of all charged
ionization products enables the channel- and fragment-specific analysis of the ionization
process. The tunable relative phase between both components of the two-color field is
an additional control parameter for the experiment. The discrepancy in the yield of lowenergy
photoelectrons for methane ionization channels with a coincident molecular ion
on the one hand and a coincident atomic ion on the other hand resembles similar results
from experiments in molecular hydrogen, which could be explained by autoionization
and simultaneous vibrational relaxation of a molecular Rydberg state. Despite the lack of
reference data for Rydberg states of methane with excitations higher than n = 6, it was
possible to estimate their energies and for one ionization channel, it could be demonstrated
that electrons released by autoionization of Rydberg states between n = 9 and n = 12 are
the origin of the enhanced low-energy electron yield.
