The TDHF method with no free parameters successfully reproduces key features of the $^{208}\text{Pb} + ^{208}\text{Pb}$ reaction. This confirms that TDHF is a viable and promising microscopic tool for heavy-ion collision phenomena. The theory was tested in Kr-induced reactions and applied to a previously underexplored mass region. The author thanks P. Bonche for his critical review and B. S. Nilsson for his collaboration. Financial support from the Danish Research Council and the Japan World Exposition Commemorative Association is acknowledged. The work was conducted at the Centre d'Etudes Nucléaires de Saclay. The paper also discusses free-free transitions following six-photon ionization of xenon atoms. Using a retarding potential technique, the energy spectrum of electrons produced by multiphoton ionization was analyzed. A model based on inverse bremsstrahlung shows reasonable agreement with experiments. The results indicate that the energy of emitted electrons is influenced by the gradient of the electromagnetic field. The maximum energy gained by electrons depends on the intensity of the laser. For the fundamental frequency, the maximum energy was about 4 eV, while for the second harmonic, it was about 0.2 eV. The results show a peak at 2 eV, close to the energy of six-photon ionization of xenon, and a secondary peak at 4.5 eV, consistent with the energy of one photon plus the ionization energy. These results suggest that a seven-photon process involving one free-free transition has been detected. The paper also reports differential cross sections for the elastic scattering of positrons by argon atoms. The measurements were made using a time-of-flight technique. The results show the differential cross sections for positrons with mean energies of 2.2, 3.4, 6.7, and 8.7 eV scattered through angles between 20° and 60° by argon atoms. The experimental errors are discussed, and the results are compared with recent theoretical calculations. The paper concludes that the measurement is the first to detect an additional photon absorption beyond the minimum number necessary for ionization of an atom.The TDHF method with no free parameters successfully reproduces key features of the $^{208}\text{Pb} + ^{208}\text{Pb}$ reaction. This confirms that TDHF is a viable and promising microscopic tool for heavy-ion collision phenomena. The theory was tested in Kr-induced reactions and applied to a previously underexplored mass region. The author thanks P. Bonche for his critical review and B. S. Nilsson for his collaboration. Financial support from the Danish Research Council and the Japan World Exposition Commemorative Association is acknowledged. The work was conducted at the Centre d'Etudes Nucléaires de Saclay. The paper also discusses free-free transitions following six-photon ionization of xenon atoms. Using a retarding potential technique, the energy spectrum of electrons produced by multiphoton ionization was analyzed. A model based on inverse bremsstrahlung shows reasonable agreement with experiments. The results indicate that the energy of emitted electrons is influenced by the gradient of the electromagnetic field. The maximum energy gained by electrons depends on the intensity of the laser. For the fundamental frequency, the maximum energy was about 4 eV, while for the second harmonic, it was about 0.2 eV. The results show a peak at 2 eV, close to the energy of six-photon ionization of xenon, and a secondary peak at 4.5 eV, consistent with the energy of one photon plus the ionization energy. These results suggest that a seven-photon process involving one free-free transition has been detected. The paper also reports differential cross sections for the elastic scattering of positrons by argon atoms. The measurements were made using a time-of-flight technique. The results show the differential cross sections for positrons with mean energies of 2.2, 3.4, 6.7, and 8.7 eV scattered through angles between 20° and 60° by argon atoms. The experimental errors are discussed, and the results are compared with recent theoretical calculations. The paper concludes that the measurement is the first to detect an additional photon absorption beyond the minimum number necessary for ionization of an atom.