Route to Direct Multiphoton Multiple Ionization

We address the concept of direct multiphoton multiple ionization in atoms exposed to intense, short wavelength radiation and explore the conditions under which such processes dominate over the sequential. Their contribution is shown to be quite robust, even under intensity fluctuations and interaction volume integration, and reasonable agreement with experimental data is also found.Comment: Close to the version to be published in Phys. Rev. A. Additional supplementary material can be found ther

Two-photon excitation and relaxation of the 3d-4d resonance in atomic Kr

Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes

Theory of multiple ionization of xenon under strong XUV radiation and the role of the giant resonance

International audienceWe examine the conditions under which multiple ionization of Xenon, under strong radiation of photon energy 93 eV and pulse duration 10 fs, leading up to Xe 21+ can be observed. Through a set of rate equations, we show that the dominant sequential channels are sufficient for and consistent with the observed ionic species. Addressing the possible role of the giant resonance in this context, we evaluate the evolution of the neutral which is responsible for that resonance, examining its depletion during the pulse. We show that, owing to the large value of the cross section and in combination with the pulse duration, as the intensity rises towards the peak value, the neutral is depleted very early, at lower intensities, thus precluding its exposure to the higher peak intensities above 10 15 W/cm 2. But we do point out that under much shorter pulse duration, direct many-electron multiple ejection may be a possibility, but not under the presently available conditions of intensity and pulse duration at the FEL (Free Electron Laser) facilities. Theory of Multiple Ionization of Xenon under strong XUV radiation and the role of the Giant Resonance.

Fe+ ion irradiation induced changes in structural and magnetic properties of iron films

490 keV Fe+ ion irradiation of 200 nm thick Fe films was found to induce both structural and magnetic changes. Both, the lattice constant and the grain size increase as a function of dose and both properties follow the same power law. Irradiation induces a depth dependent magnetic profile consisting of two sublayers. The top Fe sublayer has a magnetic moment higher than that of the Fe before the irradiation whereas the bottom sublayer lower. The two sublayers are connected with the effects of Fe+ irradiation, i.e. the top sublayer with the depth in which mainly radiation damage occurs whereas the bottom one with the implantation of impinging Fe+ ions. The magnetic moments of the two sublayers have a non-monotonous variation with irradiation dose depicting a maximum for the top sublayer and a minimum for the bottom one at 96.2 dpa (‘displacements per atom’). The magnetic moment enhancement/reduction is discussed in relation with the atomic volume variation in the case of atom displacements and/or implantation effects. © 201

Fe+ ion irradiation induced changes in structural and magnetic properties of iron films

490keV Fe+ ion irradiation of 200nm thick Fe films was found to induce both structural and magnetic changes. Both, the lattice constant and the grain size increase as a function of dose and both properties follow the same power law. Irradiation induces a depth dependent magnetic profile consisting of two sublayers. The top Fe sublayer has a magnetic moment higher than that of the Fe before the irradiation whereas the bottom sublayer lower. The two sublayers are connected with the effects of Fe+ irradiation, i.e. the top sublayer with the depth in which mainly radiation damage occurs whereas the bottom one with the implantation of impinging Fe+ ions. The magnetic moments of the two sublayers have a non-monotonous variation with irradiation dose depicting a maximum for the top sublayer and a minimum for the bottom one at 96.2 dpa (‘displacements per atom’). The magnetic moment enhancement/reduction is discussed in relation with the atomic volume variation in the case of atom displacements and/or implantation effects

Magnetic effects induced by self-ion irradiation of Fe films

Iron magnetic moment enhancement is observed following the irradiation of iron films with 490 keV Fe+ at room temperature. The iron magnetic moment enhancement increases to saturation with irradiation dose. The enhanced magnetic moment decays exponentially to its value before the irradiation with a time constant of 5.2 months. The iron magnetic moment enhancement is attributed to the creation of vacancy clusters having a concentration of about 20%, whereas the relaxation effects is attributed to the dissociation of these clusters. © 2016 American Physical Society

Magnetic effects induced by self-ion irradiation of Fe films

International audienceIron magnetic moment enhancement is observed following the irradiation of iron films with 490 keV Fe$^+$ at room temperature. The iron magnetic moment enhancement increases to saturation with irradiation dose. Theenhanced magnetic moment decays exponentially to its value before the irradiation with a time constant of 5.2 months. The iron magnetic moment enhancement is attributed to the creation of vacancy clusters having a concentration of about 20 %, whereas the relaxation effects is attributed to the dissociation of these clusters