Pedro Luis Grande

Bio: Pedro Luis Grande is an academic researcher from Universidade Federal do Rio Grande do Sul. The author has contributed to research in topics: Ion & Stopping power (particle radiation). The author has an hindex of 28, co-authored 190 publications receiving 2786 citations. Previous affiliations of Pedro Luis Grande include Rutgers University & Australian National University.

Improved charge-state formulas

Abstract: A large set of experimental charge-state distributions is analyzed in this work. Two fit formulas are presented for mean equilibrium charge states of projectiles ranging from protons to uranium. One formula is given for all ions in gas targets and another one for solid targets. The deviation from the experimental data is reduced by roughly a factor of two in comparison with the widely used formula by Nikolaev and Dmitriev as well as with the Bohr stripping criterion as revised by Northcliffe. Finally, the influence of the projectile charge state on the prediction of stopping powers for fast projectiles in carbon is shown and comparison is made with experimental energy-loss data.

Impact-parameter dependence of the electronic energy loss of fast ions

Abstract: In this work we describe a model for the electronic energy loss of bare ions at high velocities. Starting from first-order perturbation theory we propose a simple formula to calculate the impact-parameter dependence of the electronic energy loss for all impact parameters. The physical inputs are the electron density and oscillators strengths of the atoms. A very good agreement is obtained with full first-order calculations.

Femtosecond dynamics – snapshots of the early ion-track evolution

Abstract: The energy dissipation and femtosecond dynamics due to fast heavy ions in matter is critically reviewed with emphasis on possible mechanisms that lead to material modifications. Starting from a discussion of the initial electronic energy-deposition processes, three basic mechanisms for the conversion of electronic into atomic energy are investigated by means of Auger-electron spectroscopy. Results for amorphous Si, amorphous C and polypropylene are presented and discussed. Experimental evidence for a highly charged track region as well as for hot electrons inside tracks is shown. As follows mainly from Auger-electron spectroscopy, there are strong indications for different track-production mechanisms in different materials.

A unitary convolution approximation for the impact-parameter dependent electronic energy loss

Abstract: In this work, we propose a simple method to calculate the impact-parameter dependence of the electronic energy loss of bare ions for all impact parameters. This perturbative convolution approximation (PCA) is based on first-order perturbation theory, and thus, it is only valid for fast particles with low projectile charges. Using Bloch's stopping-power result and a simple scaling, we get rid of the restriction to low charge states and derive the unitary convolution approximation (UCA). Results of the UCA are then compared with full quantum-mechanical coupled-channel calculations for the impact-parameter dependent electronic energy loss.

The unitary convolution approximation for heavy ions

Abstract: The convolution approximation for the impact-parameter dependent energy loss is reviewed with emphasis on the determination of the stopping force for heavy projectiles. In this method, the energy loss in different impact-parameter regions is well determined and interpolated smoothly. The physical inputs of the model are the projectile-screening function (in the case of dressed ions), the electron density and oscillators strengths of the target atoms. Moreover, the convolution approximation, in the perturbative mode (called PCA), yields remarkable agreement with full semi-classical-approximation (SCA) results for bare as well as for screened ions at all impact parameters. In the unitary mode (called UCA), the method contains some higher-order effects (yielding in some cases rather good agreement with full coupled-channel calculations) and approaches the classical regime similar as the Bohr model for large perturbations (Z/v≫1). The results are then used to compare with experimental values of the non-equilibrium stopping force as a function of the projectile charge as well as with the equilibrium energy loss under non-aligned and channeling conditions.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Resistive switching memories based on metal oxides: mechanisms, reliability and scaling

Abstract: With the explosive growth of digital data in the era of the Internet of Things (IoT), fast and scalable memory technologies are being researched for data storage and data-driven computation. Among the emerging memories, resistive switching memory (RRAM) raises strong interest due to its high speed, high density as a result of its simple two-terminal structure, and low cost of fabrication. The scaling projection of RRAM, however, requires a detailed understanding of switching mechanisms and there are potential reliability concerns regarding small device sizes. This work provides an overview of the current understanding of bipolar-switching RRAM operation, reliability and scaling. After reviewing the phenomenological and microscopic descriptions of the switching processes, the stability of the low- and high-resistance states will be discussed in terms of conductance fluctuations and evolution in 1D filaments containing only a few atoms. The scaling potential of RRAM will finally be addressed by reviewing the recent breakthroughs in multilevel operation and 3D architecture, making RRAM a strong competitor among future high-density memory solutions.

Recoil-ion momentum spectroscopy

Abstract: High-resolution recoil-ion momentum spectroscopy (RIMS) is a novel technique to determine the charge state and the complete final momentum vector of a recoiling target ion emerging from an ionizing collision of an atom with any kind of radiation. It offers a unique combination of superior momentum resolution in all three spatial directions of with a large detection solid angle of . Recently, low-energy electron analysers based on rigorously new concepts and reaching similar specifications were successfully integrated into RIM spectrometers yielding so-called `reaction microscopes'. Exploiting these techniques, a large variety of atomic reactions for ion, electron, photon and antiproton impact have been explored in unprecedented detail and completeness. Among them kinematically complete experiments on electron capture, single and double ionization in ion - atom collisions at projectile energies between 5 keV and 1.4 GeV have been carried out. Double photoionization of He has been investigated at energies close to the threshold up to . At the contributions to double ionization after photoabsorption and Compton scattering were separated kinematically for the first time. These and many other results will be reviewed in this paper. In addition, the experimental technique is described in some detail and emphasis is given to envisaging the rich future potential of the method in various fields of atomic collision physics with atoms, molecules and clusters.

LISE++: Radioactive beam production with in-flight separators

Abstract: The program LISE ++ is designed to predict intensity and purity for future experiments using radioactive beams with in-flight separators, and for tuning experiments where its results can be quickly compared to on-line data. The name LISE ++ denotes the new generation of the LISE program, in which any separator can be built through the use of different sections labeled “blocks”. Its user-friendly interface can be used to quickly construct many separator configurations from the available blocks. The LISE ++ package already includes configuration files for most of the existing fragment and recoil separators such as the A1900 and the S800 at the NSCL, LISE3 at GANIL, FRS and SuperFRS at GSI, BigRIPS and RIPS at RIKEN. Projectile fragmentation, fusion–evaporation, fusion–fission, Coulomb fission, abrasion–fission and two body reactions models are included in this program and can be used as the production reaction mechanism to simulate experiments at beam energies above the Coulomb barrier. This program can be downloaded free of charge from the following web site: .