Rescattering effects in laser-assisted electron-atom bremsstrahlung

Rescattering effects in nonresonant spontaneous laser-assisted electron-atom bremsstrahlung (LABrS) are analyzed within the framework of time-dependent effective-range (TDER) theory. It is shown that high energy LABrS spectra exhibit rescattering plateau structures that are similar to those that are well-known in strong field laser-induced processes as well as those that have been predicted theoretically in laser-assisted collision processes. In the limit of a low-frequency laser field, an analytic description of LABrS is obtained from a rigorous quantum analysis of the exact TDER results for the LABrS amplitude. This amplitude is represented as a sum of factorized terms involving three factors, each having a clear physical meaning. The first two factors are the exact field-free amplitudes for electron-atom bremsstrahlung and for electron-atom scattering, and the third factor describes free electron motion in the laser field along a closed trajectory between the first (scattering) and second (rescattering) collision events. Finally, a generalization of these TDER results to the case of LABrS in a Coulomb field is discussed

Effect of Elliptically Polarized Light on the Angular Distribution of Photoelectrons

The angular distribution of photoelectrons predicted for elliptically polarized light is shown to be the same as that predicted for partially polarized light having incoherent perpendicular electric field components equal to the electric field components along the major and minor axes of the ellipse. Includes Corrigendum from J. Phys. B: Atom. Molec. Phys. 12:23 (1979), p. 3993

Overexpression of the nerve growth factor-inducible PC3 immediate early gene is associated with growth inhibition

PC3 (pheochromocytoma cell-3) is an immediate early gene isolated as sequence induced in the rat PC12 cell line during neuronal differentiation by nerve growth factor (NGF). PC3, which is expressed in vivo in the neuroblast when it ceases proliferating and differentiates into a neuron, has partial homology with two antiproliferative genes, BTG1 and Tob. Here we report that overexpression of PC3 in NIH3T3 and PC12 cells leads to marked inhibition of cell proliferation. In stable NIH3T3 clones expressing PC3, the transition from G1 to S phase was impaired, whereas the retinoblastoma (RB) protein was detected as multiple isoforms of M(r) 105,000-115,000 (indicative of a hyperphosphorylated state) only in low-density cultures. Such findings are consistent with a condition of growth inhibition. Thus, PC3 might be a negative regulator of cell proliferation, possibly acting as a transducer of factors influencing cell growth and/or differentiation, such as NGF, by a RB-dependent pathway. This is the first evidence of a NGF-inducible immediate early gene displaying antiproliferative activity

Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse

The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys. Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry

Polarization control of direct (non-sequential) two-photon double ionization of He

An ab initio parametrization of the doubly-differential cross section (DDCS) for two-photon double ionization (TPDI) from an s2 subshell of an atom in a 1S0-state is presented. Analysis of the elliptic dichroism (ED) effect in the DDCS for TPDI of He and its comparison with the same effect in the concurrent process of sequential double ionization shows their qualitative and quantitative differences, thus providing a means to control and to distinguish sequential and non-sequential processes by measuring the relative ED parameter

Plateau Structure in Resonant Laser-Assisted Electron-Atom Scattering

Orders of magnitude increases are predicted in the cross sections for electron-atom scattering accompanied by absorption or emission of n laser photons for incident electron energies at which the electron, by emitting μ laser photons, can be captured by the atom to form a negative ion. Enhancements are most significant in the plateau region (n \u3e\u3e μ) of the scattered electron spectrum, whose shape is predicted to replicate that of the ion’s (n + μ)-photon detachment spectrum

Circular dichroism at equal energy sharing in photo-double-ionization of He

Interference between dipole and quadrupole transition amplitudes in photo-double-ionization of He by an elliptically polarized vuv photon is shown to induce circular dichroism in the case of equal energy sharing. The magnitude of this retardation-induced dichroic effect is estimated and its impact on the nondipole asymmetries of the triply differential cross section is demonstrated

A pilot study of intralesional methotrexate injections versus triamcinolone acetonide in patients affected by nail matrix psoriasis

Nail disorders in general are difficult to treat and often frustrating, and this is also the case with nail psoriasis, especially when it is limited to the nails, and not affecting joints. The quality of life of patients with nail psoriasis is negatively affected, owing to the chronic course of the disease and frequent relapses. The purpose of this study was to compare treatment response and maintenance of response during follow-up of 12 patients with nail matrix psoriasis limited to a few nails, who were treated with intralesional injections of either methotrexate (MTX) 25 mg/mL or triamcinolone acetonide 10 mg/mL. Patients were treated every 6 weeks for 24 weeks and followed up for 6 months. Photographic documentation and assessment by Nail Psoriasis Severity Index were performed during each treatment session and at each follow-up visit. At the end of the four treatment sessions, all patients had improvement of their disease, which continued during follow-up, especially for the MTX-treated group

Coulomb Corrections in Photoelectron Spectra in the Adiabatic Limit

A momentum-dependent Coulomb correction to the probability of nonlinear ionization in a strong low-frequency laser field is derived analytically in the adiabatic limit, when the quasi-static tunneling model applies. Obtained formulas show that the Coulomb modification of photoelectron spectra can be significant both in linearly and circularly polarized fields. For linear polarization, it leads to a relative enhancement of the ionization probability for photoelectron energies of the order of the ponderomotive energy. This Coulomb effect is expected to be most significant for atomic species with relatively low ionization potentials, such as alkali atoms