The Classical Dynamic Behaviors Of H₂ In Intense Laser Fields With The Structure-Preserving Method

In recent years, with the rapid development of laser technologies, especially the progress in femto-second laser pulses, the peak intensity of laser pulses has reached and even exceeded that of the Coulomb field in a hydrogen atom. Under the action of such strong pluses, a series of phenomena which can no longer be interpreted by the conventional perturbation theory occurs.Molecular ionization and dissociation in the strong laser fields are the focus of attention of the people. Although the molecular dynamics in the laser fields is very complex, the experimental results have alarming regularities. It is difficult to use quantum theory for solving the problems of the micro-system. The classical theory and quantum theory are not entirely opposite; they only focus on the different aspects of the same things. So we can use the classical theory to solve the problems. In addition, we use the symplectic method during the process of the numerical solution. It has more advantages than the traditional R-K method and the improved R-K method.In this paper, one-dimensional molecular hydrogen has been studies. Based on the classical theory, the symplectic method has been used to study the one-dimensional molecular hydrogen in the strong laser fields. We mainly carry out the following research work: 1D model of H2 is used, with the bare Coulomb potential replaced by a screened potential to avoid the singularities at close electron–proton encounters. The initial conditions are chosen at random in the field-free case, and then the Hamiltonian canonical equations of H2 system in the intense laser field are solved numerically by means of the symplectic method under these initial conditions. We discuss the probabilities of H₂⁺ , H₂²⁺,H⁺,H in the one-color and two-color laser field. We will have the following conclusions. The positions of the electrons and the distance between the nuclei cannot stretch too far in space before the laser pulse's imposition no matter how long the time is. Since the electron is much lighter than the proton, the field-induced dissociation will take much longer time than the field-induced ionization. Once the second electron is ionized, the rate of separation speeds up.Besides, we also calculate the probabilities of ionization, dissociation and Coulomb explosion of the HD system in the two-color laser field,and get the following conclusion: Compared to the classical dynamics of H2, we find that they present similar classical dynamics quantitatively. However, the ionization channel of HD opened earlier than that of H2, but the dissociation and Coulomb explosion channels opened later at the same condition. We suppose that it is because the nucleus of HD is heavier than H2, so the two nucleuses can't be separated from each other so quickly.