Study Of Photon Momentum Partition In Strong Laser Fieldlonization Of Atoms

In the complexions of physical research area, interaction of light and matter is an eternal subject. Ever since the explanation of photoelectric effect by Ein-stein adopting a light quanta view, this subject has developed into a new stage. Especially with the invention of Lasers in1960s, when the intensity of laser field continuously grows, leading to the comparability of electron-light interaction with the inner electron-core Coulomb interaction, the over involved quantum perturbation theory in early research is not available anymore. Under the influ-ence of intense laser light, such nonlinear,non-perturbative processes as above threshold ionization, high-order harmonic generation and non-sequential dou-ble (multiple) ionization will be found in atoms(molecules). New phenomena requires of new theoretical methods, and investigation of new physical process will always leads to a new understanding of physical reality and may help the progress of new technology.Chapter one is the introductory part of this thesis. In this chapter, a short history of intense-field physics and review of lasers are given. Meanwhile, some typical processes are introduced. And two examples are given, showing how intense-filed physics can help diagnosing the sub-atomic electron dynamics.Chapter two and three concern the often-invoked research method of intense-field physics at present. The methods of time-dependent Schrodinger equation, strong-field approximation, time-dependent Newton’s equation and Keldysh theory are shortly reviewed in chapter two. Among these, time-dependent Schrodinger equation is the most reliable and fundamental theoretical method. However, due to its incapability of disentangling physical process and large numerical calculation amount, some kinds of approximation are always in place. Keldysh theory is important in its mathematical contents, and contributes much to the the early development of intense-field area. In chapter three, the details of semi-classical rescattering model are given. Based on the widely-accepted three-step scheme, we first construct an ensemble of particles using quantum tunneling theory whose subsequent dynamics is governed by Newton’s equation of motion. This method has its advantages, such as back analysis of trajectories, and has its place in strong-field physics area.Chapter four and five discuss photon-momentum partition during atomic ionization process. In chapter four, the semi-classical model is extended to in-clude the motion of ions. The electric and magnetic components of a laser field are all taken into account. Photon momentum partition between electron and ion in single atomic ionization of neon is investigated, along with some subcy-cle dynamics. It is found that in both the tunneling and rescattering process, Coulomb attraction between the ion and electron plays a role in the momentum partitioning. The effect is especially important for linearly polarized light since the photons that lift the electron out of the bound state do not always contribute to the forward ion momentum. The results in this chapter may have important implications in generation of terahertz radiation and calibration of tunnel exit by measuring final ion longitudinal momentum. Chapter five concentrates on photon momentum partition in Helium double ionization. The results show that due to the largeness of ion mass compared with electron, the electron wavepack-et drifts further along the laser propagation direction than the ion, which leads to consequences that the electron will convey part of its momentum to the ion during recollision. And also confirmed is that this kind of momentum exchange in closely related to the mechanism of double ionization, which means, through a simple calculation, that sequential double ionization, recollision impact ion-ization and recollision excited with subsequent ionization will contribute to the final electron momentum along the laser propagation direction differently.In chapter six we give a conclusion of this thesis and look forward to some future development in intense-field physics.