Classical and quantum-mechanical treatments of nonsequential double ionization with few-cycle laser pulses

We address nonsequential double ionization induced by strong, linearly polarized laser fields of only a few cycles, considering a physical mechanism in which the second electron is dislodged by the inelastic collision of the first electron with its parent ion. The problem is treated classically, using an ensemble model, and quantum-mechanically, within the strong-field and uniform saddle-point approximations. In the latter case, the results are interpreted in terms of "quantum orbits", which can be related to the trajectories of a classical electron in an electric field. We obtain highly asymmetric electron momentum distributions, which strongly depend on the absolute phase, i.e., on the phase difference between the pulse envelope and its carrier frequency. Around a particular value of this parameter, the distributions shift from the region of positive to that of negative momenta, or vice-versa, in a radical fashion. This behavior is investigated in detail for several driving-field parameters, and provides a very efficient method for measuring the absolute phase. Both models yield very similar distributions, which share the same physical explanation. There exist, however, minor discrepancies due to the fact that, beyond the region for which electron-impact ionization is classically allowed, the yields from the quantum mechanical computation decay exponentially, whereas their classical counterparts vanish.Comment: 12 pages revtex, 12 figures (eps files

Numerical solution of linear models in economics: The SP-DG model revisited

In general, complex and large dimensional models are needed to solve real economic problems. Due to these characteristics, there is either no analytical solution for them or they are not attainable. As a result, solutions can be only obtained through numerical methods. Thus, the growing importance of computers in Economics is not surprising. This paper focuses on an implementation of the SP-DG model, using Matlab,developed by the students as part of the Computational Economics course. We also discuss some of our teaching/learning experience within the course, given for the first time in the FEP Doctoral Programme in Economics.SP-DG Model, Output, Inflation, Numerical Simulation, Teaching of Economics

Internova e-learning platform in an entrepreneurial context

Currently, there is still an opposition of teachers to the implementation of new technologies in an educational context. Although several studies point out the relevance of the use of information and communication technologies in pedagogical practices, providing educational contexts more focused on learning practices and fostering more active and autonomous professionals. In this context, this article emphasizes the purpose of using Information and Communication Technologies (ICT), as well as virtual learning environments, in the higher education system, to support the teaching-learning processes. In this article, a state of the art was carried out, in order to demonstrate some advantages of the teaching-learning process, the teacher's and student behaviour profiles and its role in relation to the use of new technologies. The objective of this study was to analyse the impact of using a digital platform on the teaching-learning process in an educational context. An e-learning digital platform, INTERNOVA, developed within the scope of the INTERNOVAMARKET-FOOD project (0437_internovamarket-food_1_E - Internovamarket accelerator program to increase the competitiveness of the food sector in Galicia-Northern), within the curricular unit of Food Safety and Certification of the Master in Food Engineering's curriculum. In order to assess the impact of the training course on the students' learning outcomes, a survey was applied to master's students and Food Engineering research fellows (participants). The same survey was applied before the training and after it in order to compare both results. At the end of each training course, another survey was addressed to all the participants asking about the organization, quality and the easiness of the platform. The results obtained show that the students had no difficulties in using the platform, having revealed that they would like to continue using it more frequently. The data obtained are an evidence of the participants' learning improvement and their involvement in the learning process through the INTERNOVA platform. With this work, it can be concluded that the ICT applied to a curricular program can be a very important support in the teaching-learning process. In this context, it is important to recommend well-designed curricular programs so that teachers can improve their teaching practices, enhancing students' digital skills, and thus contributing to the development of more active and autonomous professionals. © Proceedings of the 14th IADIS International Conference e-Learning 2020, EL 2020 - Part of the 14th Multi Conference on Computer Science and Information Systems, MCCSIS 2020. All rights reserved.This work was supported by INTERREG V-A Espanha-Portugal (POCTEP) 2014-2020 (0437_INTERNOVAMARKET-FOOD_1_E) under the development of the project entitled “INTERNOVAMARKET-FOOD – Programa acelerador para aumentar a competitividade do sector alimentar da Galiza-Norte de Portugal”info:eu-repo/semantics/publishedVersio

Non-sequential double ionization below laser-intensity threshold: Anticorrelation of electrons without excitation of parent ion

Two-electron correlated spectra of non-sequential double ionization below laser-intensity threshold are known to exhibit back-to-back scattering of the electrons, viz., the anticorrelation of the electrons. Currently, the widely accepted interpretation of the anticorrelation is recollision-induced excitation of the ion plus subsequent field ionization of the second electron. We argue that another mechanism, namely simultaneous electron emission, when the time of return of the rescattered electron is equal to the time of liberation of the bounded electron (the ion has no time for excitation), can also explain the anticorrelation of the electrons in the deep below laser-intensity threshold regime. Our conclusion is based on the results of the numerical solution of the time-dependent Schr\"{o}dinger equation for a model system of two one-dimensional electrons as well as an adiabatic analytic model that allows for a closed-form solution.Comment: 6 pages and 3 figure