Using a semiclassical close-coupling approach, we have calculated electron capture, excitation and ionization cross sections for collisions of fully stripped hydrogen, helium and lithium ions with atomic hydrogen in the ground state and in all excited states up to n=3. The cross sections for collision energies between 1 and 100 keV/u are given in table form. Furthermore, we provide estimates of the accuracy of the cross sections. The set of data presented in this work represent the first complete and consistent quantum study of these collision systems and will find use in the modeling and diagnosis of thermonuclear fusion plasma reactors.

We report a detailed analysis of electron-helium scattering in the presence of a laser field; focusing on the elastic process of helium atoms from the ground state 11S. The process under investigation is dealt with a nonperturbative approach using the Volkov wave function to describe the incident and scattered electrons, while the laser–target interaction is treated by using the Floquet method. The interaction of the incident electron with the atomic target is treated within the first Born approximation. Our results are perfectly consistent with the experimental data of DeHarak et al and with the Kroll–Watson approximation results for both one and two photon emission. We have investigated the effect of nonresonant and near resonant laser field on the electron–helium elastic collision process. It was found that the differential cross section is sensitive to the intensity and the frequency of the laser field. In the case of a non resonant laser field, dressing effects are important at small scattering angles. For a near-resonant laser photon energy, those effects are strongly reduced in the forward direction.

We investigate the total cross sections of the electron transfer process in the protonhydrogen collisional system involving initial excited states at impact energies in the 2.5 eV /u−100 keV /u range. The calculations are based on two non-perturbative treatments, namely the semiclassical Atomic Orbitals Close-coupling (SC-AOCC) approach and the Classical Trajectory Monte Carlo (CTMC) method. The results are presented and discussed for the collisions H + + H(n = 1, 2, 3) taking into account the degeneracy of each level in orbital momentum. We find that the SC-AOCC results show empirical n 3 and n 4 scaling laws at low and high impact velocities, respectively.

High-order harmonic generation is a nonlinear process that converts the gained energy during light-matter interaction into high-frequency radiation, thus resulting in the generation of coherent attosecond pulses in the XUV and soft x-ray regions. Here, we propose a control scheme for enhancing the efficiency of HHG process induced by an intense near-infrared (NIR) multi-cycle laser pulse. The scheme is based on introducing an infrared (IR) single-cycle pulse and exploiting its characteristic feature that manifests by a non-zero displacement effect to generate high-photon energy. The proposed scenario is numerically implemented on the basis of the time-dependent Schrödinger equation. In particular, we show that the combined pulses allow one to produce high-energy plateaus and that the harmonic cutoff is extended by a factor of 3 compared to the case with the NIR pulse alone. The emerged high-energy plateaus is understood as a result of a vast momentum transfer from the single-cycle field to the ionized electrons while travelling in the NIR field, thus leading to high-momentum electron recollisions. We also identify the role of the IR single-cycle field for controlling the directionality of the emitted electrons via the IR-field induced electron displacement effect. We further show that the emerged plateaus can be controlled by varying the relative carrier-envelope phase between the two pulses as well as the wavelengths. Our findings pave the way for an efficient control of light-matter interaction with the use of assisting femtosecond single-cycle fields.

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