Ellipticity of High-Order Harmonics Generated by Aligned Homonuclear Diatomic Molecules Exposed to an Orthogonal Two-Color Laser Field

We investigate emission rate and ellipticity of high-order harmonics generated exposing a homonuclear diatomic molecule, aligned in the laser-field polarization plane, to a strong orthogonally polarized two-color (OTC) laser field. The linearly polarized OTC-field components have frequencies r? and s?, where r and s are integers. Using the molecular strong-field approximation with dressed initial state and undressed final state, we calculate the harmonic emission rate and harmonic ellipticity for frequency ratios 1:2 and 1:3. The obtained quantities depend strongly on the relative phase between the laser-field components. We show that with the OTC field it is possible to generate elliptically polarized high-energy harmonics with high emission rate. To estimate the relative phase for which the emission rate is maximal we use the simple man’s model. In the harmonic spectra as a function of the molecular orientation there are two types of minima, one connected with the symmetry of the molecular orbital and the other one due to destructive interference between different contributions to the recombination matrix element, where we take into account that the electron can be ionized and recombine at the same or different atomic centers. We derive a condition for the interference minima. These minima are blurred in the OTC field except in the cases where the highest occupied molecular orbital is modeled using only s or only p orbitals in the linear combination of the atomic orbitals. This allows us to use the interference minima to assess which atomic orbitals are dominant in a particular molecular orbital. Finally, we show that the harmonic ellipticity, presented in false colors in the molecular-orientation angle vs. harmonic-order plane, can be large in particular regions of this plane. These regions are bounded by the curves determined by the condition that the harmonic ellipticity is approximately zero, which is determined by the minima of the T-matrix contributions parallel and perpendicular to the fundamental component of the OTC field. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Nondipole effects in terahetz-pulse-assisted strong-field ionization

Nondipole effects in processes assisted by a THz field having the strength of a few MV/cm can be significant due to its long wavelength. We illustrate this for strong-laser-field-induced ionization assisted by a THz field. To this end, we generalize our strong-field-approximation theory so that it includes the first-order term in a 1/c expansion of the vector potential. We show that in this case, in addition to a shift of the maximum of the photoelectron momentum distribution, the differential ionization probability as well as the cutoff energy can be significantly increased. For an explanation of these unexpected results we use the saddle-point method adjusted to include nondipole effects

Application of the Phase-Space Path Integral to Strong-Laser-Field-Assisted Electron-Ion Radiative Recombination: A Gauge-Covariant Formulation

We consider the problem of the choice of gauge in nonrelativistic strong-laser-field physics. For this purpose, we use the phase-space path-integral formalism to obtain the momentum-space matrix element of the exact time-evolution operator. With the assumption that the physical transition amplitude corresponds to transitions between eigenstates of the physical energy operator rather than the unperturbed Hamiltonian H0=(−i∂/∂r)2/2+V(r), we prove that the aforementioned momentum-space matrix elements obtained in velocity gauge and length gauge are equal. These results are applied to laser-assisted electron-ion radiative recombination (LAR). The transition amplitude comes out identical in length gauge and velocity gauge, and the expression agrees with the one conventionally obtained in length gauge. In addition to the strong-field approximation (SFA), which is the zeroth-order term of our expansion, we present explicit results for the first-order and the second-order terms, which correspond to LAR preceded by single and double scattering, respectively. Our general conclusion is that in applications to atomic processes in strong-field physics the length-gauge version of the SFA (and its higher-order corrections) should be used. Using the energy operator as the basis-defining Hamiltonian, we have shown that the resulting transition amplitude is gauge invariant and agrees with the form commonly derived in length gauge

The role of a pharmacist in pharmacovigilance system

Introduction: Although they represent an important mediator between patients and National Pharmacovigilance Centre, pharmacists still don't participate enough in system of reporting adverse drug reactions (ADR). By reporting ADR both quality of therapy and quality of patient's life are improving, and pharmaceutical industry is also encouraged to invent and produce new formulations which will be better beared and whose use will significantly improve risk-benefi t ratio. Aim: The aim of this work is that by collecting information about ADRs, based on direct contact of a pharmacist and patients, explain and improve the role of a pharmacist in pharmacovigilance system. Subjects and Methods: Information about adverse reactions were being collected in three private pharmacies in Inđija and in one private pharmacy in Sombor. In period from 20.12.2017.-10.01.2018. pharmacists collected data about adverse reactions of medicines. In period from 11.01.-01.02.2018. patients were additionally informed about unexpected and adverse drug reactions. The standard form for reporting an adverse reaction, which was taken from the site of Medicines and Medical Devices Agency of Serbia (ALIMS), was fi lled for each reported case and sent to National Pharmacovigilance Center (NPC). Suspect drugs were classified in categories according to Anatomical-Therapeutic-Chemical classification (ATC). Results: In first period, there were 19 reported reactions. After additional information given to patients, there were 33 reported adverse reactions. The most numerous adverse drug reactions were reported for the group of cardiovascular drugs (32.7%), the group of anti-infective drugs with systemic effects (15.4%) and for group of drugs which affect nervous system (13.5%). After analyzing reported reactions, according to NPC all of reactions were expected (52), but 3 of them fulfilled criteria of seriousness. Conclusions: Thanks to additional information and direct communication between a pharmacist and patients, reporting unexpected and adverse drug reactions is significantly improving