Dynamics of atom-diatom reactions at the low energy regime

The 8th International Meeting on Photodynamics and Related Aspects, Oaxaca, México, Oct 26-31, 2014. Conferencia invitadaThe dynamics of some atom-diatom reactions has been investigated in the low collision energy regime (Ecoll < 10^-1 eV). The possibility of complex-forming mechanisms is analyzed by means of a statistical quantum method in comparison with quantum mechanical results and experimental measurements. The case of the H^+ + H_2 reaction, and isotopic variants, for which a significant dependence on the energy range has been reported before, is treated in detail. Recent studies on the D^+ + H_2 reaction found theoretical rate coefficients in a good agreement with experiment down to 10^-3 eV . Similar investigations in other reactions such as Li+YbLi and He+NeH^+ are discussed.Peer Reviewe

Low energy complex-forming dynamics on atom-diatom reactions

QRS XIII, Salamanca (Spain), July 6th to 10th, 2015; http://fama.iff.csic.es/con/QRS-2015Peer Reviewe

Estructura y dinámica de fotodisociación de complejos triatómicos débilmente ligados : los sistemas He79 Br2 y 4He3

Estudio de la fotodisociación del complejo de van der Waals He79Br2 mediante un cálculo tridimensional exacto y aproximaciones de tipo diabático y adiabático. Asimismo se emplea el método de estabilización para el estudio y caracterización de las resonancias del sistema. Mediante un proceso de promediado térmico de las transiciones rotacionales relevantes se comparan las distribuciones rotacionales producto teóricas con las obtenidas experimentalmente. El estudio del 4He3 se lleva a cabo mediante un cálculo variacional exacto con el que se obtienen las energías de los dos estados vibracionales ligados y las correspondientes funciones de onda. El trabajo incluye el estudio del comportamiento Efimov del estado excitado

Path integral Monte Carlo investigations on doped helium clusters

32 págs.; 21 figs.; 5 tabs.One of the most commonly employed methods to study doped helium clusters is the path integral Monte Carlo (PIMC) approach. In this review we present results of recent investigations on a series of both atomic and diatomic dopants attached to droplets formed with up to 40 He atoms. Besides the comparison with similar studies existing in the literature, this work also gives the possibility to analyse different issues such as the role played by the He¿impurity interaction in the overall geometry of the clusters, the inclusion of internal molecular degrees of freedom and the exchange permutation symmetry in the PIMC calculations. The study of the structure and energies of and at thermal equilibrium presented in this work thus covers most of the usual aspects treated for these kinds of doped systems. © 2016 Taylor & Francis GroupThis work was supported by MICINN under FIS2011-29596-C02-01 and FIS2014-51933-P.Peer Reviewe

A configurational study of helium clusters doped with He∗− and He2 ∗−

9 pags.; 10 figs.; 4 tabs.Helium clusters doped with electronically excited atomic and molecular helium anions He∗− and He∗− 2 at T = 0.4 K are studied by means of path integral Monte Carlo calculations. Geometry and energetics of the systems with up to 32 solvating He atoms are characterised. The interactions between the anions and the neutral He atoms have been described by fitting previously reported ab initio points to analytical expressions. The HeN–He∗− clusters with N > 6 display a structure defined by a bipyramid which completely solvates the atomic anion, whereas the rest of surrounding He atoms form a dimple around that initial cage. On the contrary, the structures observed for the HeN–He∗−2 clusters clearly show the dopant located outside the helium droplet, thereby confirming the heliophobic character of He∗− 2. C 2015 AIP Publishing LLCThis work has been supported by MICINN Grant No. FIS2011-29596-C02-01. R.R.-C. acknowledges funding from Grant No. JAE-Pre-2010-01277. F.A.G. acknowledges several helpful discussions with A. Mauracher and thanks him for providing us with the original computed ab initio points for the He–dopant interactionsPeer Reviewe

Quantum Zeno-based control mechanism for molecular fragmentation

A quantum control mechanism is proposed for molecular fragmentation processes within a scenario grounded on the quantum Zeno effect. In particular, we focus on the van der Waals Ne-Br$_2$ complex, which displays two competing dissociation channels via vibrational and electronic predissociation. Accordingly, realistic three dimensional wave packet simulations are carried out by using ab initio interaction potentials recently obtained to reproduce available experimental data. Two numerical models to simulate the repeated measurements are reported and analyzed. It is found that the otherwise fast vibrational predissociation is slowed down in favor of the slow electronic (double fragmentation) predissociation, which is enhanced by several orders of magnitude. Based on these theoretical predictions, some hints to experimentalists to confirm their validity are also proposed.Comment: 4 pages, 3 figure

Erratum: >A comparative study of the Si+O2\SiO+O reaction dynamics from quasiclassical trajectory and statistical based methods> [J. Chem. Phys. 128, 174307 (2008)]

Peer Reviewe

Fármacos multidiana en el posible tratamiento de la esclerosis lateral amiotrófica

La esclerosis lateral amiotrófica (ELA) es una enfermedad neurodegenerativa en la que se produce la muerte de las motoneuronas superiores e inferiores. Aunque tiene un origen desconocido y multifactorial, en el 97% de los pacientes se ha encontrado depósitos de agregados de la proteína TDP-43 (proteína TAR de unión a ADN/ARN). Las funciones de esta proteína nuclear se centran en la regulación del ARN. La proteinopatía de TDP-43 se desencadena con la translocación del núcleo al citoplasma y su hiperfosforilación, lo que da lugar a la acumulación de agregados proteicos y consiguiente degeneración neuronal. Las quinasas que participan en este proceso de fosforilación son: GSK3, CK1, TTBK, CDC7. En este trabajo se propone la modulación de varias quinasas simultáneamente para conseguir un efecto farmacológico más eficaz. Para ello se han evaluado fármacos multidiana, con inhibición dual simultánea en dos de las cuatro quinasas mencionadas, así como combinaciones de monoterapias. Los resultados obtenidos han mostrado sinergia en los tratamientos y validan la utilización de fármacos multidiana en patologías complejas como la EL

Rotational state-changing collisions between N2+_2^+ and Rb at low energies

We present a theoretical study of rotationally elastic and inelastic collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin temperature regime prevalent in ion-atom hybrid trapping experiments. The cross sections for rotational excitation and de-excitation collisions were calculated using quantum-scattering methods on ab-initio potential energy surfaces for the energetically lowest singlet electronic channel of the system. We find that the rotationally inelastic collision rates are at least an order of magnitude smaller than the charge-exchange rates found in this system, rendering inelastic processes a minor channel under the conditions of typical hybrid trapping experiments.Comment: 6 pages, 5 figures, Computational study of rotational state changing collision

Investigating transition state resonances in the time domain by means of Bohmian mechanics: The F+HD reaction

In this work, we investigate the existence of transition state resonances on atom-diatom reactive collisions from a time-dependent perspective, stressing the role of quantum trajectories as a tool to analyze this phenomenon. As it is shown, when one focusses on the quantum probability current density, new dynamical information about the reactive process can be extracted. In order to detect the effects of the different rotational populations and their dynamics/coherences, we have considered a reduced two-dimensional dynamics obtained from the evolution of a full three-dimensional quantum time-dependent wave packet associated with a particular angle. This reduction procedure provides us with information about the entanglement between the radial degrees of freedom (r,R) and the angular one (\gamma), which can be considered as describing an environment. The combined approach here proposed has been applied to study the F+HD reaction, for which the FH+D product channel exhibits a resonance-mediated dynamics.Comment: 12 pages, 9 figure