Classical Trajectory Dynamics Of Particle Collision In The Presence Of Intense Laser Fields

Since the "nuclear structure model" was successfully put forward in the a particle scat-tering experiment,particle collision has gradually become an important approach for human beings to understand particle-interaction and explore their internal structure and dynamics.In atomic and molecular physics,people study the ionization and excitation properties of atoms and molecules through particles collision method.In condensed matter physics,the internal states of crystals are obtained by experiments of electron diffraction,neutron diffraction and X-ray crystal diffraction.In the high energy physics,particle collision is also a powerful tool for people to explore the elementary particles.Recently,with the development of laser technolo-gy,especially the generation and development of the chirped pulse amplification technology in 1980s,the electric field of laser field can be easily compared with the Coulomb effect of atomic nucleus electrons.Such strong laser field will have a huge influence on particles collision.The laser field will affect the scattering cross section of electron or other particles colliding with atom.In the laser-atoms interaction,the high harmonic generation promotes the development of atto-second science.Recently,the processes of laser-assisted nuclear reaction are also the interested issues.With the development of experimental technology,most physical phenomena need to be explained and described by theoretical research.However,the theoretical method based on quantum mechanics is difficult to be used in the multi-body calculation involving the interaction of multiple particles,and the classical trajectory Monte Carlo method based on Newtonian mechanics has many shortcomings in multi-body calculation due to its own classical characteristics.The development of more complete theoretical calculation method to describe the physical mechanism behind the experimental observation is the most important task in to-day's study.This work focuses on establishing and improving the classical trajectory Monte Carlo method,and makes a series of interesting explorations around the ionization problem of parti-cle collisions.We consider the particle collision issues in laser field,such as electron-atom col-lision,positron-atom collision,recollision of the ionization electron and the deuterium-tritium collision.The main works are listed as follows:1.We develop a spin dependent classical trajectory Monte Carlo approach to investigate the spin-tagged collisional ionization process.With the help of anti-symmetrized Gaussian wave packets,an effective interaction potential between the two spin-tagged electrons is de-rived to mimic the spin associated quantum effect of Pauli exclusion principle.Our model is applied to investigate the spin dependent collisional ionization of e-H system.The results are in good agreement with experimental data,ab-initio quantum-mechanical calculations as well as a variety of characteristics of the Wannier theory for near-threshold ionization.Further applica-tions of our model to laser-assisted collisional ionization are demonstrated and some interesting results are presented.2.We investigate the fragmentation dynamics of hydrogen atom impacted by a positron whose energy is just above the atomic ionization potential(i.e.,near threshold),using a classical trajectory Monte Carlo approach combined with a Heisenberg potential.The cross sections of various fragmentation channels are calculated with addressing the Wannier threshold law that depicts the impact energy dependent cross section for the three-body breakup channel.In particular,we investigate the collision configurations for individual fragmentation channel and calculate the correlated spectrum of the angular distribution and energy allocation of the outgoing electron and positron to uncover the mechanism of their highly imbalanced energy partition.Finally,we extend to study the positron-hydrogen collisions in the presence of an external electromagnetic field and show that the fractions of three different channels,i.e.,three-body breakup,Positronium formation,and Rydberg excitation,can be considerably modulated with a laser pulse of peak intensity as weak as 1011W/cm2.3.The triple ionization of the interaction between laser and lithium atom is studied by the improved classical trajectory Monte Carlo method.We obtained the shell structure and the stable ground state configuration of lithium atom and calculate the total ionization probability of lithium in the range of 1013W/cm2 to 1017W/cm2.The difference between sequential triple ionization and non sequential triple ionization is described in detail by plotting the momentum distribution of Li3+ ions after ionization.According to the energy distribution of three electrons mapped in the Dalitz diagram,three types of recollision mechanism of non sequential triple ionization are explained.4.We develop a semiclassical approach to investigate the deuterium tritium fusion cross sections in the presence of intense laser field at none-relativistic condition.The barrier pen-etrability of deuterium-tritium collision has been concerned by using the classical trajectory simulation with the help of the Wentzel-Kramers-Brillouin approximation.We find that such penetrability is significantly enhanced due to the scheme that quiver motion induced by intense laser field effectively increasing the incident nuclei kinetic energy.As a consequence,the cross sections of DT fusion process have been effectively improved around initial energies region 5-25keV of experimental concerned.Finally,we give a summary of the thesis and give a perspective on the promising directions in the depth application of the classical trajectory Monte Carlo method.