Lithium Ionization by a Strong Laser Field

We study ab initio computations of the interaction of Lithium with a strong laser field. Numerical solutions of the time-dependent fully-correlated three-particle Schroedinger equation restricted to the one-dimensional soft-core approximation are presented. Our results show a clear transition from non-sequential to sequential double ionization for increasing intensities. Non sequential double ionization is found to be sensitive to the spin configuration of the ionized pair. This asymmetry, also found in experiments of photoionization of Li with synchrotron radiation, shows the evidence of the influence of the exclusion principle in the underlying rescattering mechanism

Recreational fisheries in rural regions of the South-Western Iberian peninsula: a case study

La dimensión humana de la pesca deportiva ha ganado interés en todo el mundo durante la última década para la correcta gestión de los recursos naturales. Sin embargo, en muchas regiones rurales del sur de Europa, los aspectos sociales y económicamente de la pesca deportiva siguen siendo poco estudiados. En este estudio se realizó una encuesta para cubrir esta brecha de conocimientos y elaborar recomendaciones de manejo potenciales para la explotación adecuada. Una encuesta de la pesca recreativa se llevó a cabo durante la temporada de pesca 2008-2009. Los datos se recogieron siguiendo los procedimientos de la encuesta de nasas y las respuestas a 171 entrevistas fueron analizadas para 27 variables. Para asociar estas variables categóricas se realizó un análisis de componentes principales (CATPCA). En el eje CATPCA en primer lugar (44,24% de la varianza), las correlaciones entre las variables mostraron una dimensión "económica". Las variables más influyentes en esta dimensión fueron los gastos, la temporada y el número de días de pesca por año, junto con la distancia recorrida a los sitios de pesca. La segunda dimensión (24,47% de la varianza) estaba relacionada con las especies preferidas, el equipo necesario para la captura de ellos, y con la facilidad de acceso a los sitios donde se encuentran estas especies. Los datos mostraron algunas diferencias entre los pescadores jóvenes y mayores con respecto a las variables analizadas.The human dimension of recreational fishing has gained interest worldwide during the last decade for proper management of the natural resources. However, in many rural regions in Southern Europe, the social and economically aspects of recreational fishing remains poorly studied. In this study we conducted a survey to cover this gap of knowledge and draw potential management recommendations for proper exploitation. A survey of recreational fishing was conducted during the 2008-2009 fishing seasons. Data were collected following creel survey procedures and responses to 171 interviews were analyzed for 27 variables. To associate these variables a categorical principal components analysis (CATPCA) was performed. On the first CATPCA axis (44.24% of variance), the correlations among variables showed an “economic” dimension. The most influential variables in this dimension were expenditure, the season, and number of fishing days per year, together with the distance travelled to fishing sites. The second dimension (24.47% of variance) was related to the preferred species, the gear necessary to catch them, and with facility off access to sites where these species are found. The data showed some differences between both young and old fishermen with respect to the variables analyzed.-- Junta de Extremadura. Servicio de Medio AmbientepeerReviewe

Saturation spectroscopy in optically thick three-level gas media

High-contrast transmission spectra arising from saturated absorption in optically thick Doppler-broadened three-level media are analyzed within the formalism of Maxwell-Bloch-type equations. It is found that although in the strong pumping engine propagation-induced line narrowing and light-shift elimination occur, spectral features lying within the natural linewidth cannot be resolved

Valley in the efficiency of the high-order harmonic yield at ultra-high laser intensities

We study the process of high-order harmonic generation using laser pulses with non-adiabatic turn-on and intensities well above saturation. As a main point, we report the existence of a valley structure in the efficiency of single-atom high-order harmonic generation with increasing laser intensities. Consequently, after an initial decrease, the high-frequency radiation yield is shown to increase for higher intensities, returning to a level similar to the case below saturation. Such behavior contradicts the general belief of a progressive degradation of the harmonic emission at ultrahigh intensities, based on the experience with pulses with smoother turn-on. We shall show that this behavior corresponds to the emergence of a new pathway for high-order harmonic generation, which takes place during the pulse turn-on. Our study combines trajectory analysis, wavelet techniques and the numerical integration of 3-Dimensional Time Dependent Schrödinger Equation. The increase in efficiency raises the possibility of employing ultrahigh intensities to generate high-frequency radiation beyond the water window.Spanish Ministerio de Ciencia e Innovación through the Consolider Program SAUUL ( CSD2007-00013) and research project FIS2009-09522, from Junta de Castilla y León through the Program for Groups of Excellence (GR27) and from the EC’s Seventh Framework Programme ( LASERLAB-EUROPE, grant agreement n 228334)

Dipole spectrum structure of non-resonant non-pertubative driven two-level atoms

We analize the dipole spectrum of a two-level atom excited by a non-resonant intense monochromatic field, under the electric dipole approximation and beyond the rotating wave approximation. We show that the apparently complex spectral structure can be completely described by two families: harmonic frequencies of the driving field and field-induced nonlinear fluorescence. Our formulation of the problem provides quantitative laws for the most relevant spectral features: harmonic ratios and phases, non-perturbative Stark shift, and frequency limits of the harmonic plateau. In particular, we demonstrate the locking of the harmonic phases at the wings of the plateau opening the possibility of ultra-short pulse generation through harmonic filtering

Fundamental studies on electron dynamics in exact paraxial beams with angular momentum

© 2022 by the authors. I.P. acknowledges support from Ministerio de Ciencia, Innovacion y Universidades (Spain) under Projects RTI2018-100835-B-I00 (MCIU/AEI/FEDER, UE) and RTI2018-096967-B-I00. R.F.A.-E. acknowledges support from Ministerio de Ciencia, Innovacion y Universidades (Spain) under Project PGC2018-094684-B-C21 (contract partially funded by FEDER). L.R. acknowledges support from Laserlab V (Grant Agreement No. 871124, European Union Horizon 2020 INFRAIA research and innovation program), from IMPULSE (Grant Agreement No. 871161, European Union Horizon 2020 INFRADEV research and innovation program), and from Junta de Castilla y Leon Grant No. CLP087U16. R.F.A.-E. and F.C. are associate members of Instituto de Biocomputacion y Fisica de los Sistemas Complejos, Universidad de Zaragoza, Zaragoza, Spain.Classical electromagnetic radiation with orbital angular momentum (OAM), described by nonvanishing vector and scalar potentials (namely, Lorentz gauge) and under Lorentz condition, is considered. They are employed to describe paraxial laser beams, thereby including non-vanishing longitudinal components of electric and magnetic fields. The relevance of the latter on electron dynamics is investigated in the reported numerical experiments. The lowest corrections to the paraxial approximation appear to have a negligeable influence in the regimes treated here. Incoherent Thomson scattering (TS) from a sample of free electrons moving subject to the paraxial fields is studied and investigated as a beam diagnosis tool. Numerical computations elucidate the nature and conditions for the so called trapped solutions (electron motions bounded in the transverse plane of the laser and drifting along the propagation direction) in long quasi-steady laser beams. The influence of laser parameters, in particular, the laser beam size and the non-vanishing longitudinal field components, essential for the paraxial approximation to hold, are studied. When the initial conditions of the electrons are sufficiently close to the origin, a simplified model Hamiltonian to the full relativistic one is introduced. It yields results comparing quite well quantitatively with the observed amplitudes, phase relationships and frequencies of oscillation of trapped solutions (at least for wide laser beam sizes). Genuine pulsed paraxial fields with OAM and their features, modeling true ultra-short pulses are also studied for two cases, one of wide laser beam spot (100 p.m) and other with narrow beam size of 6.4 p.m. To this regard, the asymptotic distribution of the kinetic energy of the electrons as a function of their initial position over the transverse section is analyzed. The relative importance of the transverse structure effects and the role of longitudinal fields is addressed. By including the full paraxial fields, the asymptotic distribution of kinetic energy of an electron population distributed across the laser beam section, has a nontrivial and unexpected rotational symmetry along the optical propagation axis.Depto. de Física TeóricaFac. de Ciencias FísicasTRUEUnión Europea. H2020Ministerio de Ciencia e Innovación (MICINN)/ FEDERJunta de Castilla y Leonpu

Coherent population trapping in two-electron three-level systems with aligned spins

The possibility of coherent population trapping in two electron states with aligned spins (orthosystem) is evidenced. From the analysis of a three-level atomic system containing two electrons, and driven by the two laser fields needed for coherent population trapping, a conceptually new kind of dark state appears. The properties of this trapping are physically interpreted in terms of a dark hole, instead of a dark two-electron state. This technique, among many other applications, offers the possibility of measuring, with subnatural resolution, some superposition-state matrix elements of the electron-electron correlation that due to their time dependent nature are inaccessible by standard measuring procedures

Ultrafast lasers: A new frontier for optical materials processing

In the last years, ultrashort laser pulses have gone through the laboratory walls to burst into the industrial arena as a tool for material micro- and nanoprocessing. The number of industrial fields and specific applications is steadily growing, reaching the nanotechnology applications. Now, we celebrate the 25th anniversary of the CPA (chirped pulse amplification) technique which made available intense ultrashort (subpicosecond) pulses able to induce ablation of any material. This contribution tries to review the fundamentals of ultrafast lasers as well as some of their applications, emphasizing the processing of optical materials.We acknowledge support from Junta de Castilla y León (GR27), from Ministerio de Ciencia e Innovación (Consolider SAUUL CSD2007-00013 and Grant FIS2009-09522), from EU 7FP, LaserLab-Europe-2 (Grant Agreement No. 228334) and ELI Preliminary Phase. The authors acknowledge support from CLPU (Ultrashort Ultraintense Pulsed Laser Centre), a new spanish research facility funded by Ministerio de Ciencia e Innovación, Junta de Castilla y León and Universidad of Salamanca, which is giving beam access to the domestic and international scientific community

Spatiotemporal evolution of light during propagation in filamentation regime

The full description of the evolution of light during its nonlinear propagation represents a valuable help to the complete understanding of important nonlinear phenomena such as light filamentation. In this paper we present a comparison between theoretical and experimental results of the spatiotemporal structure of a light filament at different propagation distances. In order to obtain the experimental spatiotemporal structure, we have used a technique based on spatially resolved spectral interferometry called STARFISH, for spatiotemporal amplitude-and-phase reconstruction by Fourier transform of interference spectra of high-complex beams. We have been able to observe important nonlinear pulse dynamics during the nonlinear propagation, including pulse splitting and the subsequent competition among the pulses that result from the splitting, obtaining a full insight into the general nonlinear behaviorWe acknowledge support from the Spanish Ministerio de Ciencia e Innovación through the Consolider Program Science and Applications of Ultrafast and Ultra-intense Lasers (SAUUL) (CSD2007-00013) and Research Project FIS2009-09522; from Junta de Castilla y León through the Program for Groups of Excellence (GR27) and Research Project SA002B08; and from the European Community’s Seventh Framework Programme (LASERLAB-EUROPE) grant agreement 228334). We also acknowledge support from the Centro de Laseres Pulsados (CLPU), Salamanca, Spain. B. Alonso and I. J. Sola acknowledge the support of the Spanish Ministerio de Ciencia e Innovación through the “Formación de Profesorado Universitario” and “Ramón y Cajal” grant programs, respectively