2017, Dalimier, E., Ya Faenov, A., Oks, E., Angelo, P., Pikuz, T.A., Fukuda, Y., Andreev, A., Koga, J., Sakaki, H., Kotaki, H., Pirozhkov, A., Hayashi, Y., Skobelev, I.Yu., Pikuz, S.A., Kawachi, T., Kando, M., Kondo, K., Zhidkov, A., Tubman, E., Butler, N.M.H., Dance, R.J., Alkhimova, M.A., Booth, N., Green, J., Gregory, C., McKenna, P., Woolsey, N., Kodama, R.

We present X-ray spectroscopic diagnostics in femto-second laser-driven experiments revealing nonlinear phenomena caused by the strong coupling of the laser radiation with the created plasma. Among those nonlinear phenomena, we found the signatures of the Two Plasmon Decay (TPD) instability in a laser-driven CO2 cluster-based plasma by analyzing the Langmuir dips in the profile of the O VIII Lyϵ line, caused by the Langmuir waves created at the high laser intensity 3 1018Wcm-2. With similar laser intensities, we reveal also the nonlinear phenomenon of the Second Harmonic Generation (SHG) of the laser frequency by analyzing the nonlinear phenomenon of satellites of Lyman δ and ϵ lines of Ar XVII. In the case of relativistic laser-plasma interaction we discovered the Parametric Decay Instability (PDI)-induced ion acoustic turbulence produced simultaneously with Langmuir waves via irradiation of thin Si foils by laser intensities of 1021Wcm-2.

2017, Odžak, S., Hasović, E., Milošević, D.B.

We present a theory of high-order harmonic generation by arbitrary polyatomic molecules based on the molecular strong-field approximation (MSFA) in the framework of the S-matrix theory. A polyatomic molecule is modeled by an (N + 1)-particle system, which consists of N heavy atomic (ionic) centers and an electron. We derived various versions (with or without the dressing of the initial and/or final molecular state) of the MSFA. The general expression for the T-matrix element takes a simple form for neutral polyatomic molecules. We show the existence of the interference minima in the harmonic spectrum and explain these minima as a multiple-slit type of interference. This is illustrated by numerical examples for the nitrous oxide (N2O) molecule exposed to strong linearly polarized laser field.

2017, Becker, W., Milošević, D.B.

Above-threshold ionization (ATI) of atoms by a strong bicircular laser field is investigated using the strong-field approximation and the quantum-orbit theory. The bicircular field consists of two coplanar counterrotating circularly polarized fields with a frequency ratio of 2:1. The velocity map of the angle-resolved ATI spectra, both for direct and rescattered electrons, reflects the shape of a parametric plot of the bicircular field and its symmetries. It is shown that the main characteristics of the ATI spectra can be explained using only a few quantum orbits having short travel times. We also analyze a recently discovered [Phys. Rev. A 93, 052402(R) (2016)] bicircular-field-induced spin asymmetry of the ATI electrons and show that the momentum dependence of the spin-asymmetry parameter is stronger for longer wavelengths.

2017-11-10, Schäfer, Jan, Sigeneger, Florian, Šperka, Jiří, Rodenburg, Cornelia, Foest, Rüdiger

The self-organized discharge behaviour occurring in a non-thermal radio-frequency plasma jet in rare gases at atmospheric pressure was investigated. The frequency of the azimuthal rotation of filaments in the active plasma volume and their inclination were measured along with the gas temperature under varying discharge conditions. The gas flow and heating were described theoretically by a three-dimensional hydrodynamic model. The rotation frequencies obtained by both methods qualitatively agree. The results demonstrate that the plasma filaments forming an inclination angle α with the axial gas velocity uz are forced to a transversal movement with the velocity uφ=tan(α)*uz, which is oriented in the inclination direction. Variations of ${u}_{\phi }$ in the model reveal that the observed dynamics minimizes the energy loss due to convective heat transfer by the gas flow. The control of the self-organization regime motivates the application of the plasma jet for precise and reproducible material processing.

2017, Ezhevskii, A.A., Detochenko, A.P., Soukhorukov, A.V., Guseinov, D.V., Kudrin, A.V., Abrosimov, N.V., Riemann, H.

Spin transport of conduction electrons in silicon samples doped with bismuth in the 1.1•1013 - 7.7•1015 cm-3 concentration range was studied by the Hall effect measurements. The dependence of the Hall voltage magnitude on the magnetic field is the sum of the normal and spin Hall effects. The electrons are partially polarized by an external magnetic field and are scattered by the bismuth spin-orbit potential. Spin-flip scattering results in the additional electromotive force which compensates the normal Hall effect in strong magnetic fields.

2017, Hasović, E., Becker, W., Milošević, D.B.

We investigate high-order above-threshold ionization (HATI) of krypton atoms by a bicircular laser field, which consists of two coplanar co- or counter-rotating circularly polarized fields of frequencies rw and sw. We show that the photoelectron spectra in the HATI process, presented in the momentum plane, exhibit the same discrete rotational symmetry as the driving field. We also analyze HATI spectra for various combinations of the intensities of two field components for co- and counter-rotating fields. We find that the appearance of high-energy plateau for the counter-rotating case is vary sensitive to the laser intensity ratio, while the plateau is always absent for the co-rotating bicircular field.

2017, Argenti, L., Jiménez Galán, Á., Taïeb, R., Caillat, J., Maquet, A., Martín, F.

Synopsis In contrast to one-photon transitions and non-resonant multiphoton transitions, time delay in resonant multi-photon electron emission can exhibit large positive and negative values that have no scattering equivalent, due to the interference of multiple ionization paths.

2017, Arbó, D.G., López, S. D., Kubin, M., Hummert, J., Vrakking, M.J.J., Kornilov, O.

Synopsis We present a theoretical and experimental study of the subcycle interference in laser assisted XUV ionization of Ar atoms. Averaging over the focal volume happens to blur the intracycle interference, which thus cannot be measured directly. We show that even at these conditions, the intracycle interference can be obtained through the subtraction of two different angle and energy-resolved distributions at slightly different laser intensities.

2017, You, Daehyun, Fukuzawa, Hironobu, Sakakibara, Yuta, Takanashi, Tsukasa, Ito, Yuta, Maliyar, Gianluigi G., Motomura, Koji, Nagaya, Kiyonobu, Nishiyama, Toshiyuki, Asa, Kazuki, Sato, Yuhiro, Saito, Norio, Oura, Masaki, Schöffler, Markus, Kastirke, Gregor, Hergenhahn, Uwe, Stumpf, Vasili, Gohkberg, Kirill, Kuleff, Alexander I., Cederbaum, Lorenz S., Ueda, Kiyoshi

We present an experimental evidence for a so-far unobserved, but potentially very important step relaxation cascades following inner-shell ionization of a composite system: Multiply charged ionic states created after Auger decay may be neutralized by electron transfer from a neighboring species, producing at the same time a low-energy free electron. This electron transfer-mediated decay (ETMD) called process is effective even after Auger decay into the dicationic ground state. Here, we report the ETMD of Ne2+ produced after Ne 1s photoionization in Ne-Kr mixed clusters.

2017, Arkhipov, R.M., Arkhipov, M.V., Pakhomov, A.V., Babushkin, I., Demircan, A., Morgner, U., Rosanov, N.N.

We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this medium. Possible applications in the ultrafast optics such as optical switcher and laser beam deflector are discussed.