Collective Absorption Dynamics and Enhancement in Deformed Targets

The interaction of intense fs laser pulses with thin foils that have an imposed deformation is compared with thick targets that develop bow shocks. Both target types yield good absorption. Up to 80% absorption is obtained for a $0.2\mu m$ thick, 15 times over-dense foil at $4 \cdot 10^{18} W/cm^2$. A value of 50% is obtained for a $4 \mu m$ thick, 2 times over-dense thick target at $10^{18} W/cm^2$. For comparable extension and curvature of the laser-plasma interfaces absorption levels in both targets become similar. In both absorption scales weakly with intensity and density. Energy transport in thin foils and thick targets, however, is different.Comment: 4 pages, 5 figures, Fig. 5 has been replace

Dielectric Screening In The Thomas-Fermi Model

In this paper, we investigate the dielectric screening process in the Thomas-Fermi model with several variations such as the thermal effects, relativistic effects, motion of the test charge, and the effect of a very strong magnetic field. Comparisons are made with the corresponding results in a classical plasma. Some apparently anomalous results are pointed out and explained

Electron correlation versus stabilization of atoms in intense laser pulses

We present a numerical study of the stabilization process for a fully correlated two-electron model atom in an intense laser pulse. A comparison with calculations for a "real" 3D He atom is also done. We concentrate on the very high frequency regime, where the photon energy exceeds the ionization energy of both electrons, outer and inner. Our results show that when correlation effects are included the ionization probability (IP) is enhanced. Nevertheless, we still observe a decreasing IP within a certain intensity domain. The results from the fully correlated simulations are compared with those from simpler, approximate models. The full numerical treatment for the He atom is not yet possible. We therefore present results obtained with "single active electron" approximation and time-dependent density functional theory. Our numerical simulations can be useful for the future understanding of the stabilization phenomenon for more-than-one electron atoms

The Research on Student Article and Application Problems in Tax Agreement between China and Germany

由于中国和德国之间经济交往情况以及国际形势的变化，2014年中德之间重新签订了《中华人民共和国和德意志联邦共和国对所得和财产避免双重征税和防止偷漏税的协定》（以下简称新《中德税收协定》）。新《中德税收协定》中有多处变化，其中对学生、学徒所得的课税条款（以下简称学生条款）是变化较大的一条。当今世界，教育国际化潮流已经成为不可逆的趋势，国际学生的激增，对学生条款进行分析，进而更好地适用学生条款，在教育国际化的背景下具有重要意义。其次，对学生条款的研究也有助于整个《中德税收协定》的协调统一。本文的第一部分主要介绍学生条款的界定、历史背景以及国际税收理论和实践中的学生条款，重点论述了学生条款的特殊性；...With the development of economic exchange and international situation between China and Germany, the two parties signed a new tax agreement between China and Germany in 2014, which is also officially called Agreement between The People’s Republic of China and the Federal Republic of Germany for the Avoidance of Double Taxation and the Prevention of Fiscal Evasion with Respect to Taxes of Income an...学位：法学硕士院系专业：法学院_国际法学学号：1362012115011

Collisionless absorption, hot electron generation, and energy scaling in intense laser-target interaction

Among the various attempts to understand collisionless absorption of intense ultrashort laser pulses a variety of models has been invented to describe the laser beam target interaction. In terms of basic physics collisionless absorption is understood now as the interplay of the oscillating laser field with the space charge field produced in the plasma. A first approach to this idea is realized in Brunel's model the essence of which consists in the formation of an oscillating charge cloud in the vacuum in front of the target. The investigation of statistical ensembles of orbits shows that the absorption process is localized at the ion-vacuum interface and in the skin layer: Single electrons enter into resonance with the laser field thereby undergoing a phase shift which causes orbit crossing and braking of Brunel's laminar flow. This anharmonic resonance acts like an attractor for the electrons and leads to the formation of a Maxwellian tail in the electron energy spectrum. Most remarkable results of our investigations are the Brunel-like hot electron distribution at the relativistic threshold; the minimum of absorption at $I\lambda^2 \cong (0.3-1.2)\times 10^{21}$ W/cm$^2\mu$m$^2$, in the plasma target with the electron density of $n_e \lambda^2\sim 10^{23}$cm$^{-3}\mu$m$^2;$ the drastic reduction of the number of hot electrons in this domain and their reappearance in the highly relativistic domain; strong coupling of the fast electron jets with the return current through Cherenkov emission of plasmons. The hot electron energy scaling shows a strong dependence on intensity in the moderately relativistic domain $I\lambda^2 \cong (10^{18} - 10^{20})$ W/cm$^2\mu$m$^2$, a scaling in vague accordance with current published estimates in the range $I\lambda^2 \cong (0.14-3.5)\times 10^{21}$ W/cm$^2\mu$m$^2$, and a distinct power increase beyond $I=3.5\times 10^{21}$ W/cm$^2\mu$m$^2$.Comment: 11 pages, 10 figure

Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets

We report on the first absorption experiments of sub-10 fs high-contrast Ti:Sa laser pulses incident on solid targets. The very good contrast of the laser pulse assures the formation of a very small pre-plasma and the pulse interacts with the matter close to solid density. Experimental results indicate that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees incidence angle. The simulation results of PSC PIC code clearly confirm the observations and show that the collisionless absorption works efficiently in steep density profiles