Lippmann-Schwinger description of multiphoton ionization

We outline a formalism and develop a computational procedure to treat the process of multiphoton ionization (MPI) of atomic targets in strong laser fields. We treat the MPI process nonperturbatively as a decay phenomenon by solving a coupled set of the integral Lippmann-Schwinger equations. As basic building blocks of the theory we use a complete set of field-free atomic states, discrete and continuous. This approach should enable us to provide both the total and differential cross-sections of MPI of atoms with one or two electrons. As an illustration, we apply the proposed procedure to a simple model of MPI from a square well potential and to the hydrogen atom.Comment: 25 pages, 3 figure

Оценка динамики артросонографическихпоказателей при длительном лечениигонартроза Терафлексом( 3-летнее наблюдение)

Two hundred and forty-four outpatients with gonarthrosis were examined. The time course of arthrosonographic (the height of the articular cartilage, the volume of intraarticular effusion, the width of the joint cleft, and the degree of osteophytosis) changes were estimated during longterm Teraflex therapy and in control patients. The long-term (3-year) Teraflex therapy was shown to have a restraining impact on the processes of articular cartilage degradation and the progression of articular structural changes and to exert an anti-inflammatory effect.Обследовано 244 амбулаторных пациента с гонартрозом. Оценены в динамике артросонографические показатели (высота суставного хряща, объем выпота в полость сустава, ширина суставной щели, выраженность остеофитоза) на фоне длительного приема Терафлекса, а также в контроле. Показано сдерживающее влияние длительной терапии (на протяжении 3 лет) Терафлексом на процессы деградации суставного хряща, прогрессирование структурных изменений в суставах, продемонстрирован противовоспалительной эффект лечения препаратом

Experimental ionization of atomic hydrogen with few-cycle pulses

We present the first experimental data on strong-field ionization of atomic hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10% level between the data and an {\it ab initio} simulation over a wide range of laser intensities and electron energies

Calculation of the photoionization with de-excitation cross sections of He and helium-like ions

We discuss the results of the calculation of the photoionization with de-excitation of excited He and helium-like ions Li$^{+}$ and B$^{3+}$ at high but non-relativistic photon energies $\omega$. Several lower $^{1}S$ and $^{3}S$ states are considered. We present and analyze the ratios $R_{d}^{+\ast}$ of the cross sections of photoionization with de-excitation, $\sigma_{(d)}^{+\ast}(\omega)$, and of the photo-ionization with excitation, $\sigma ^{+\ast}(\omega)$. The dependence of $R_{d}^{+\ast}$ on the excitation of the target object and the charge of its nucleus is presented. Apart to theoretical interest, results obtained can be verified using such long living excited state as $2^{3}S$ of He.Comment: 10 pages, 6 table

Measuring laser carrier-envelope-phase effects in the noble gases with an atomic hydrogen calibration standard

We present accurate measurements of carrier-envelope-phase effects on ionization of the noble gases with few-cycle laser pulses. The experimental apparatus is calibrated by using atomic hydrogen data to remove any systematic offsets and thereby obtain accurate CEP data on other generally used noble gases such as Ar, Kr, and Xe. Experimental results for H are well supported by exact time-dependent Schrödinger equation theoretical simulations; however, significant differences are observed in the case of the noble gases.Griffith Sciences, School of Natural SciencesFull Tex

Correlation effects during liquid infiltration into hydrophobic nanoporous mediums

Correlation effects arising during liquid infiltration into hydrophobic porous medium are considered. On the basis of these effects a mechanism of energy absorption at filling porous medium by nonwetting liquid is suggested. In accordance with this mechanism, the absorption of mechanical energy is a result expenditure of energy for the formation of menisci in the pores on the shell of the infinite cluster and expenditure of energy for the formation of liquid-porous medium interface in the pores belonging to the infinite cluster of filled pores. It was found that in dependences on the porosity and, consequently, in dependences on the number of filled pores neighbors, the thermal effect of filling can be either positive or negative and the cycle of infiltration-defiltration can be closed with full outflow of liquid. It can occur under certain relation between percolation properties of porous medium and the energy characteristics of the liquid-porous medium interface and the liquid-gas interface. It is shown that a consecutive account of these correlation effects and percolation properties of the pores space during infiltration allow to describe all experimental data under discussion

Attosecond angular streaking and tunnelling time in atomic hydrogen

Tunnelling, one of the key features of quantum mechanics, ignited an ongoing debate about the value, meaning and interpretation of 'tunnelling time'. Until recently the debate was purely theoretical, with the process considered to be instantaneous for all practical purposes. This changed with the development of ultrafast lasers and in particular, the 'attoclock' technique that is used to probe the attosecond dynamics of electrons. Although the initial attoclock measurements hinted at instantaneous tunnelling, later experiments contradicted those findings, claiming to have measured finite tunnelling times. In each case these measurements were performed with multi-electron atoms. Atomic hydrogen (H), the simplest atomic system with a single electron, can be 'exactly' (subject only to numerical limitations) modelled using numerical solutions of the 3D-TDSE with measured experimental parameters and acts as a convenient benchmark for both accurate experimental measurements and calculations. Here we report the first attoclock experiment performed on H and find that our experimentally determined offset angles are in excellent agreement with accurate 3D-TDSE simulations performed using our experimental pulse parameters. The same simulations with a short-range Yukawa potential result in zero offset angles for all intensities. We conclude that the offset angle measured in the attoclock experiments originates entirely from electron scattering by the long-range Coulomb potential with no contribution from tunnelling time delay. That conclusion is supported by empirical observation that the electron offset angles follow closely the simple formula for the deflection angle of electrons undergoing classical Rutherford scattering by the Coulomb potential. Thus we confirm that, in H, tunnelling is instantaneous (with an upperbound of 1.8 as) within our experimental and numerical uncertainty.Comment: 7 figure

Positron scattering on atoms and molecules

An overview is given of recent progress in the calculation of positron scattering on atoms and molecules using the convergent close-coupling method. Particular emphasis is given to those cases where positronium formation is one of the reaction channels, as well as the importance of demonstrating convergence with increasing orbital angular momentum of the bases used. Targets considered are atomic hydrogen, lithium, and molecular hydrogen