Emergence of Classical Orbits in Few-Cycle Above-Threshold Ionization

The time-dependent Schr\"odinger equation for atomic hydrogen in few-cycle laser pulses is solved numerically. Introducing a positive definite quantum distribution function in energy-position space, a straightforward comparison of the numerical ab initio results with classical orbit theory is facilitated. Integration over position space yields directly the photoelectron spectra so that the various pathways contributing to a certain energy in the photoelectron spectra can be established in an unprecedented direct and transparent way.Comment: 4 pages, 4 figures REVTeX (manuscript with higher resolution figures available at http://www.dieterbauer.de/publist.html

Analysis of two-dimensional high-energy photoelectron momentum distributions in single ionization of atoms by intense laser pulses

We analyzed the two-dimensional (2D) electron momentum distributions of high-energy photoelectrons of atoms in an intense laser field using the second-order strong field approximation (SFA2). The SFA2 accounts for the rescattering of the returning electron with the target ion to first order and its validity is established by comparing with results obtained by solving the time-dependent Schr\"{o}dinger equation (TDSE) for short pulses. By analyzing the SFA2 theory, we confirmed that the yield along the back rescattered ridge (BRR) in the 2D momentum spectra can be interpreted as due to the elastic scattering in the backward directions by the returning electron wave packet. The characteristics of the extracted electron wave packets for different laser parameters are analyzed, including their dependence on the laser intensity and pulse duration. For long pulses we also studied the wave packets from the first and the later returns.Comment: 12 pages, 10 figure

Epidemiološki značaj određivanja olova, kadmija, bakra i cinka u kosi i trajnim zubima osoba koje žive u blizini topionice olova

In this paper the content of lead, cadmium, copper and zinc was analysed by atomic absorption spectrophotometry (model Unicam SP 90), in the hair of 200 persons residing in the immediate vicinity (within a distance of 5 km) of a lead smeltery and in a control group of 200 persons living at a distance greater than 10 km from the main air pollution source. Statistically significant differences in the content of the metals were found, the probability range being 0.05-0.01. The concentration of lead, cadmium, copper and zinc in permanent teeth was also analysed in relation to the distance of the residence from the lead smeltery in a group of 111 persons living 1-5 km from it and in 23 persons living in the area 20 to 30 km away. The established differences were statistically significant for all analysed metals with the exception of zinc.Autori iznose rezultate merenja sadržaja olova, kadmija, bakra i cinka u 200 uzoraka kose muškaraca i žena koji žive u blizini topionice olova i u uzorcima kose jednakog broja kontrolnih osoba koje žive daleko od topionice olova. Olovo, kadmij, bakar i cink određivani su atomskom apsorpcijskom spektrofotometrijom. Nađene su značajne razlike u koncentraciji ispitivanih metala između eksponirane i kontrolne skupine (p<0,05 i p<0,01). Koncentracije olova, kadmija, bakra i cinka merene su i u trajnim zubima 111 osoba koje žive u blizini topionice kao i u zubima 23 kontrolne osobe koje žive daleko od topionice. I u ovim su uzorcima utvrđene statistički značajne razlike u koncentracijama svih metala osim cinka između dviju ispitivanih grupa

Non-dipole recollision-gated double ionization and observable effects

Using a three-dimensional semiclassical model, we study double ionization for strongly-driven He fully accounting for magnetic field effects. For linearly and slightly elliptically polarized laser fields, we show that recollisions and the magnetic field combined act as a gate. This gate favors more transverse - with respect to the electric field - initial momenta of the tunneling electron that are opposite to the propagation direction of the laser field. In the absence of non-dipole effects, the transverse initial momentum is symmetric with respect to zero. We find that this asymmetry in the transverse initial momentum gives rise to an asymmetry in a double ionization observable. Finally, we show that this asymmetry in the transverse initial momentum of the tunneling electron accounts for a recently-reported unexpectedly large average sum of the electron momenta parallel to the propagation direction of the laser field.Comment: Amended the focus of the paper and discussion. 9 pages, 7 figure

Goodness--of--Fit Tests Based on the Min--Characteristic Function

We propose tests of fit for classes of distributions that include the Weibull, the Pareto and the Fr\'echet, distributions. The new tests employ the novel tool of the min--characteristic function and are based on an L2--type weighted distance between this function and its empirical counterpart applied on suitably standardized data. If data--standardization is performed using the MLE of the distributional parameters then the method reduces to testing for the standard member of the family, with parameter values known and set equal to one. We investigate asymptotic properties of the tests, while a Monte Carlo study is presented that includes the new procedure as well as competitors for the purpose of specification testing with three extreme value distributions. The new tests are also applied on a few real--data sets

Molecular imaging using high-order harmonic generation and above-threshold ionization

Accurate molecular imaging via high-order harmonic generation relies on comparing the harmonic emission from a molecule and an adequate reference system. However, an ideal reference atom with the same ionization properties as the molecule does not always exist. We show that for suitably designed, very short laser pulses, a one-to-one mapping between high-order harmonic frequencies and electron momenta in above-threshold ionization exists. Comparing molecular and atomic momentum distributions then provides the electron return amplitude in the molecule for every harmonic frequency. We show that the method retrieves the molecular recombination transition moments highly accurately, even with suboptimal reference atoms.Comment: 5 pages, 4 figure

(Giant) Vortex - (anti) vortex interaction in bulk superconductors: The Ginzburg-Landau theory

The vortex-vortex interaction potential in bulk superconductors is calculated within the Ginzburg-Landau (GL) theory and is obtained from a numerical solution of a set of two coupled non-linear GL differential equations for the vector potential and the superconducting order parameter, where the merger of vortices into a giant vortex is allowed. Further, the interaction potentials between a vortex and a giant vortex and between a vortex and an antivortex are obtained for both type-I and type-II superconductors. Our numerical results agree asymptotically with the analytical expressions for large inter-vortex separations which are available in the literature. We propose new empirical expressions valid over the full interaction range, which are fitted to our numerical data for different values of the GL parameter

Macroscopic aspects of relativistic x-ray assisted high-order harmonic generation

A theoretical model is developed describing high-order harmonic generation (HHG) from a gas of multiply-charged ions driven by a laser field of relativistic intensity. Macroscopic propagation of harmonics is investigated in a relativistic HHG setup where the relativistic drift is suppressed by means of x-ray field assistance of the driving laser field. The possibility of phase-matched emission of the harmonics is shown. The laser field geometry is optimized to maximize the HHG yield with the corresponding phase-matching schemes. Crucial issues determining the macroscopic HHG yield are discussed in detail

Nuclear signatures in high-harmonic generation from laser-driven muonic atoms

High-harmonic generation from muonic atoms exposed to intense laser fields is considered. Our particular interest lies in effects arising from the finite nuclear mass and size. We numerically perform a fully quantum mechanical treatment of the muon-nucleus dynamics by employing modified soft-core and hard-core potentials. It is shown that the position of the high-energy cutoff of the harmonic spectrum depends on the nuclear mass, while the height of the spectral plateau is sensitive to the nuclear radius. We also demonstrate that $\gamma$-ray harmonics can be generated from muonic atoms in ultrastrong VUV fields, which have potential to induce photo-nuclear reactions.Comment: 5 pages, 3 figure