Xuhai Hong

Electron dynamics in Na4 clusters under femtosecond laser irradiation

The electron dynamics in metal clusters under femtosecond laser irradiation yield excited nonlinear phenomena under the control of laser parameters. In this study, metal clusters Na4 as an example under femtosecond laser irradiation have been observed within the framework of time-dependent density functional theory molecular dynamics (TDDFT-MD), which self-consistently couples a quantum-mechanical TDDFT treatment of valence electrons with a classical molecular dynamics description of ionic cores. The specific excitation frequencies and polarization directions of the laser have been chosen to investigate the behavior of the dipole response and ionization process. We found that it is necessary to explore the electron dynamics of metal clusters by matching the laser frequency and polarization direction. In addition, resonant dipole oscillations induced by suitable laser parameters show pronounced enhancement of the ionization behavior.

Theoretical investigation of the electron capture and loss processes in the collisions of He2+ + Ne

Based on the time-dependent density functional theory, a method is developed to study ion-atom collision dynamics, which self-consistently couples the quantum mechanical description of electron dynamics with the classical treatment of the ion motion. Employing real-time and real-space method, the coordinate space translation technique is introduced to allow one to focus on the region of target or projectile depending on the actual concerned process. The benchmark calculations are performed for the collisions of He(2+) + Ne, and the time evolution of electron density distribution is monitored, which provides interesting details of the interaction dynamics between the electrons and ion cores. The cross sections of single and many electron capture and loss have been calculated in the energy range of 1-1000 keV/amu, and the results show a good agreement with the available experiments over a wide range of impact energies.

An effective method for state population within time-dependent density functional theory.

The determination of state population probability within the framework of time-dependent density functional theory (TDDFT) has remained a widely open question. The aim of this study is to find out whether and how this probability can be extracted from time-dependent density, which has been used as the basic variable within TDDFT. We propose an effective method to calculate state population probabilities, which has been well validated in benchmark case studies on nonresonant (detuned) Rabi oscillations of a Na atom, Na2 dimer, and Na4 cluster irradiated by a monochromatic laser.

Theoretical study of small silicon clusters: Optical absorption spectra and dipole polarizabilities of Si n (n=2−7)

The optical absorption spectra of Sin (n=2−7) clusters have been systematically calculated within the framework of time-dependent density functional theory (TDDFT). In addition, calculated dipole polarizabilities of Sin (n=2−7) clusters based on density functional theory (DFT) are very good agreement with other theoretical results. It is suggested that the geometry structure of clusters can be identified by optical absorption spectra and dipole polarizabilities.