Rueckstreuung und Zerstaeubung beim Beschuss von ungeordneten Medien mit leichten Ionen

SIGLETIB Hannover: DR 7473 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Ablation of opaque surfaces due to laser irradiation

The time-dependent ablation process of a metal surface due to laser irradiation is investigated for the case of high Peclet numbers. An analytical solution of the energy balance equation is found by the method of characteristics. The theory is restricted to the geometrical-optical approximation. There exist self-similar solutions which are piecewise parabolic in space. Their amplitude is damped which finally leads to a smoothed quasistationary surface profile. An expression for the decay time of this solution is derived which depends on the amplitude and the length of periodicity

Scattering of fast H-2 molecules from Pd surfaces:Classical trajectory simulations

Classical trajectories simulations have been carried out for H-2 molecules at energies from a few hundred eV up to a few keV scattering under grazing incidence from Pd surfaces of distinct crystallographic orientation. Emphasis is laid on the importance of collisional dissociation mechanisms for incidence along surface semi-channels and along highly indexed directions. The initial molecule orientation is found to be decisive for the dissociation probability. Distributions of the center-of-mass energy and the angular momentum of the scattering products suggest that collisional dissociation is rotationally induced for channeling conditions, the molecule axis being initially oriented at an angle with the beam. For off-channeling incidence, collisional dissociation is vibrationally induced, the molecule axis being initially perpendicular to the surface plane

Molecule scattering from solid surfaces:Orientation and surface corrugation effects

Various effects connected with orientation and surface corrugation in molecule scattering from solid surfaces are investigated by means of classical trajectories simulations for H-2 impinging on Pd(110). Primary excitation of the projectiles is modeled according to the situation in molecular beam experiments, where vibrational levels are occupied up to upsilon = 10 and more. Elastic interactions are mediated by an extended EAM potential, while inelastic effects an ignored. A correlation is found between the molecular orientation at the time of impact and the relative position of collisionally dissociated fragments. For grazing incidence along surface semichannels, rotational excitation is found with angular momentum vector parallel to the direction of flight (propeller mode). The survival probability shows no scaling with E-perpendicular to for varying energies and angles of incidence

Scattering of fast N-2 from Pd(111): Orientational influences on the interaction dynamics

Classical trajectory studies of grazing incidence, N-2 scattering from Pd(111) surfaces in the keV rang are performed. We use an analytical six-dimensional potential energy surface based on ab initio density-functional-theory-calculations and experimental data to describe the molecule-surface interaction. The simulation results are in good agreement with experimental data (time-of-flight measurements) obtained for this system. Characteristical patterns in the phase space of molecular axis orientation and relative energy of the dissociation fragments after the scattering event are found, which fit well to the results from experimental studies of the similar N-2(+) - Cu(111) system