Entity

Time filter

Source Type


Bieler C.R.,University of California at Irvine | Bieler C.R.,Albion College | Janda K.C.,University of California at Irvine | Hernandez-Lamoneda R.,Autonomous University of Morelos | Roncero O.,Institute Fisica Fundamental
Journal of Physical Chemistry A | Year: 2010

Pump-probe results are reported for NeCl2 excited to the Cl 2 B state, undergoing vibrational predissociation, and then probed via E -B transitions. Intensities, lifetimes and product vibrational branching ratios are reported for 16 ≤ v' ≤ 19 Cl2 stretching quanta. The intensity of the signal rapidly decreases above v' = 17. Detailed wave packet calculations of the vibrational predissociation dynamics are performed to determine if the experimental results can be explained by the onset of IVR dynamics. The calculations and the experiment are in close accord for low vibrational levels. For higher levels, some, but not all, of the loss of experimental signal can be attributed to IVR. To test whether electronic relaxation dynamics are important for NeCl2 and ArCl2, excited state potential surfaces that incorporate spin orbit coupling effects are calculated. These surfaces are then used in a wave packet calculation that includes both vibrational predissociation and electronic predissociation dynamics. The results show that electronic predissociation is important for ArCl2 levels above v' = 12. For NeCl2 the calculation suggests that the onset of electronic predissociation should occur for levels as low as v' = 13 but may not contribute markedly to the observed loss of signal above z/ = 17. Suggestions are made for further studies of this puzzling problem. © 2010 American Chemical Society. Source


Hernandez-Lamoneda R.,Autonomous University of Morelos | Sanz-Sanz C.,Institute Fisica Fundamental | Roncero O.,Institute Fisica Fundamental | Pio J.M.,University of California at Irvine | And 2 more authors.
Chemical Physics | Year: 2012

We present the first comprehensive ab initio study of the Ne-Br 2 potential energy surfaces and the non-adiabatic couplings between the valence excited electronic states. These ab initio results are used to obtain 3-D approximate potentials for each electronic state, and these potentials are used in a wave packet calculation of the competing electronic predissociation and vibrational predissociation dynamics. The results of this calculation are in excellent agreement with both experimental results and a previous empirical fit to the experiments. The calculations allow us to observe not only the competition between vibrational and electronic dynamics for the dimer, but also the competition between two different electronic channels. Coupling to the 2 g state dominates for the levels studied here, but coupling to the C state is progressively more important for low vibrational levels, and may dominate at levels below which the current results pertain. The ability of ab initio surfaces and couplings to so accurately reproduce experimental data raises the hope of a complete understanding of the VP and EP dynamics for other Rg-halogen dimers. Success in the case presented here is largely due to the fact that the VP dynamics for the vibrational levels in this study are in the simple, direct regime. Understanding the simple case so thoroughly provides new hope that the more complicated examples, such as ArI 2 and NeCl 2, for which experiment and theory are not currently in accord, may yet yield to analysis. © 2011 Elsevier B.V. All rights reserved. Source


Estupinn-Lopez F.H.,Grupo Mexico | Almeraya-Calderon F.,Grupo Mexico | Bautista Margulis R.G.,Juarez Autonomous University of Tabasco | Baltazar Zamora M.A.,University of Veracruz | And 3 more authors.
International Journal of Electrochemical Science | Year: 2011

The use of electrochemical noise (EN) technique for the investigation and monitoring of corrosion has allowed many interesting advances in the corrosion science in recent years. A special advantage of EN measurements includes the possibility to detect and analyses the early stages of localized corrosion. However, the understanding of the electrochemical information included in the EN signal is actually very limited. This work shows the results obtained from EN measurements for different materials that exhibit pitting corrosion. The obtained transients in potential and current time, correlates with the scanning electron microscopy (SEM) surface analysis. Electrochemical measurements were made at different exposure times in order to obtain any correlation. The used materials were austenitic 316 stainless steel and 2205 duplex alloy, immersed in ferric chloride (FeCl3) and sodium chloride (NaCl) electrolytes. SEM analysis shows that the observed transients in the time series really correspond to the activity of pit nucleation developed on the surface of the electrodes. © 2011 by ESG. Source


Gutierrez-Mercado Y.K.,University of Guadalajara | Canedo-Dorantes L.,Autonomous University of Morelos | Gomez-Pinedo U.,Neurosciences Institute | Serrano-Luna G.,Mexican Bioelectromagnetics Society | And 2 more authors.
Bioelectromagnetics | Year: 2013

It has been demonstrated that the exposure of biological systems to magnetic fields (MFs) can produce several beneficial effects: tissue recovery in chronic wounds, re-establishment of blood circulation after tissue ischemia or in necrotic tissues, improvement after epileptic episodes, angiogenesis, etc. In the current study, the effects of extremely low frequency (ELF) MF on the capillaries of some circumventricular organs (CVOs) are demonstrated; a vasodilator effect is reported as well as an increase in their permeability to non-liposoluble substances. For this study, 96 Wistar male rats (250g body mass) were used and divided into three groups of 32 rats each: a control group (no treatment); a sham ELF-MF group; and an experimental group subjected to ELF-MF (120Hz harmonic waves and 0.66mT, root mean square) by the use of Helmholtz coils. All animals were administered colloidal carbon (CC) intravenously to study, through optical and transmission electron microscopy, the capillary permeability in CVOs and the blood-brain barrier (BBB) in brain areas. An increase in capillary permeability to CC was detected in the ELF-MF-exposed group as well as a significant increase in vascular area (capillary vasodilation); none of these effects were observed in individuals of the control and sham ELF-MF groups. It is important to investigate the mechanisms involved in the phenomena reported here in order to explain the effects of ELF-MF on brain vasculature. © 2012 Wiley Periodicals, Inc. Source


Rapoport Yu.,Taras Shevchenko National University | Boardman A.,University of Salford | Grimalsky V.,Autonomous University of Morelos | Selivanov Yu.,Ukrainian Academy of Sciences | Kalinich N.,Taras Shevchenko National University
International Conference on Mathematical Methods in Electromagnetic Theory, MMET | Year: 2012

Tunable, nonlinear and active metamaterials are discussed, as a basis of optical instrumentation and signal processing such as filters, birefringent devices, lenses etc. The new method for modeling nonlinear field and energy concentrators is reported, which includes the combination of the new version of complex geometrical optics (CGO) and full-wave nonlinear electromagnetic solution (FWNES) used in different regions of a concentrator and matching of these solutions. Nonlinear concentrators based on both isotropic and hyperbolic metamaterials are discussed. The new strongly nonlinear phenomena- nonlinear focusing switching, taking place when input amplitude of concentrated rays/beams exceeds some threshold value, is found in both types of the field concentrators and searched. © 2012 IEEE. Source

Discover hidden collaborations