A5102706043- Distributed and Parallel Computing Systems
- Advanced Data Storage Technologies
- Advanced Chemical Physics Studies
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University of Chicago
2015-2024
Argonne National Laboratory
2021-2022
University of Illinois Chicago
2013
Computational Physics (United States)
2011
Naval Research Laboratory Information Technology Division
2011
Albert Ellis Institute
2010
Max Planck Institute for Dynamics and Self-Organization
1992
Max Planck Society
1989-1990
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotodissociation of water in the first absorption band: a prototype for dissociation on repulsive potential energy surfaceV. Engel, V. Staemmler, R. L. Vander Wal, F. Crim, J. Sension, B. Hudson, P. Andresen, S. Hennig, K. Weide, and SchinkeCite this: Phys. Chem. 1992, 96, 8, 3201–3213Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April...
Experimental and theoretical studies of the photodissociation single vibrational states in HOD provide a qualitative quantitative understanding dissociation dynamics bond selectivity this process. Vibrationally mediated photodissociation, which one photon prepares state that second dissociates, can selectively cleave O–H molecules containing four quanta stretching excitation. Dissociation HOD(4νOH) with 266 or 239.5-nm photons produces OD fragments at least 15 fold excess over OH, but...
The photodissociation of H2S through excitation in the first absorption band (λ≊195 nm) is investigated by means extensive ab initio calculations. Employing MRD-CI method we calculate potential energy surfaces for lowest two electronic states 1A″ symmetry varying both HS bond distances as well HSH bending angle. (In C2v point group these have 1B1 and 1A2, respectively.) lower adiabatic surface dissociative when one H atom pulled away whereas upper binding. For equilibrium angle 92° ground...
The photodissociation of H2O and D2O in the second band (λ≳120 nm) is investigated using two-dimensional (translation rotation) classical trajectories. calculations include all electronic states which are involved dissociation dynamics, i.e., B̃ 1A1, X̃ Ã 1B1. nonadiabatic transitions B̃→X̃ B̃→Ã near linearity modeled a very simple way, does not yield OH(2Σ)/OH(2Π) branching ratio. rotational distributions for OH(2Σ) OD(2Σ) agree qualitatively well with measurements. They highly inverted...
The FLASH code has evolved into a modular and extensible scientific simulation software system over the decade of its existence. During this time it been cumulatively used by thousand researchers to investigate problems in astrophysics, cosmology, some areas basic physics, such as turbulence. Recently, many new capabilities have added enable simulate high-energy density physics. Enhancements these continue, along with enhancements enabling simulations fluid-structure interactions. started...
We present the results of a three-dimensional wave packet study on photodissociation ClNO through excitation first singlet state S1. The calculations employ an ab initio potential energy surface depending Cl–N and N–O bond coordinates bending angle. By expanding in terms eigenfunctions NO rotor, time-dependent Schrödinger equation is transformed into coupled set 60 two-dimensional partial differential equations which are solved by discretization grid. yields absorption spectrum all...
We calculated the absorption spectra of H2O and D2O in second band around 128 nm using a two-dimensional ab initio potential energy surface for B̃(1A1) electronic state. Nonadiabatic coupling to lower states à X̃ vibrational degree freedom OH fragment are completely neglected. Despite these limitations agreement with measured is very satisfactory. The overall shape, width, energetical position maximum well described. Most important, however, reproduction diffuse structures superimposed on...
We describe the detonation mechanism comprising "Pulsationally Assisted" Gravitationally Confined Detonation (GCD) model of Type Ia supernovae SNe Ia. This is analogous to previous GCD reported in Jordan et al.(2008); however, chosen initial conditions produce a substantively different mechanism, resulting from larger energy release during deflagration phase. The final kinetic and nickel-56 yields conform better observational values than case for "classical" models. In present class models,...
Flash-X is a highly composable multiphysics software system that can be used to simulate physical phenomena in several scientific domains. It derives some of its solvers from FLASH, which was first released 2000. has new framework relies on abstractions and asynchronous communications for performance portability across range increasingly heterogeneous hardware platforms. meant primarily solving Eulerian formulations applications with compressible and/or incompressible reactive flows. also...
The photodissociation of H2O in the second absorption band (X̃→B̃) is investigated a completely time-dependent approach. Schrödinger equation solved by close-coupling method expanding two-dimensional wave packet terms free rotor states. vibrational degree freedom OH fragment fixed and only motion on B̃-state potential-energy surface considered. calculated spectrum exhibits long progression diffuse structures, ΔE∼0.1 eV, very good agreement with experimental spectrum. structure readily...
The photodissociation of H2 S in the first absorption band is studied by time-dependent wave packets evolving two electronic states; lower state dissociative and upper one bound. adiabatic potential energy surfaces transition dipole functions are constructed from ab initio calculations while nonadiabatic coupling adjusted. diffuse structure superimposed on broad spectrum due to symmetric stretch motion (bound) which strongly quenched coupling. This different water band.
We investigate the photodissociation of highly excited vibrational states water in first absorption band. The calculation includes an ab initio potential energy surface for Ã-state and X̃→Ã transition dipole function. bending angle is fixed at equilibrium value within ground electronic state. Most interesting high sensitivity final distribution OH on initially prepared state H2 O. At wavelengths near onset spectrum can be qualitatively understood as a Franck–Condon mapping initial O wave...
In many astrophysical simulations, both Eulerian and Lagrangian quantities are of interest. For example, in a galaxy cluster merger simulation, the intracluster gas can have discretization, while dark matter be modeled using particles. FLASH, component-based scientific simulation code, superimposes framework atop an adaptive mesh refinement to enable such simulations. The discretization field variables is Eulerian, entities occur different forms including tracer particles, massive charged...
The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between filaments of galaxy clusters to several teragauss black holes and neutron stars. standard model behind cosmological fields nonlinear amplification seed via turbulent dynamo values observed. We have conceived experiments that aim demonstrate study mechanism laboratory. Here we describe design these through simulation campaigns using FLASH, highly capable radiation magnetohydrodynamics...
Advances in modeling and algorithms, combined with growth computing resources, have enabled simulations of multiphysics–multiscale phenomena that can greatly enhance our scientific understanding. However, on currently available high-performance (HPC) maximizing the outcome requires many trade-offs. In this paper we describe experiences running explosion phase Type Ia supernovae largest platforms. The use FLASH, a modular, adaptive mesh, parallel simulation code wide user base. multiple...
The Biermann Battery effect is frequently invoked in cosmic magnetogenesis and studied High-Energy Density laboratory physics experiments. Generation of magnetic fields by the due to mis-aligned density temperature gradients smooth flow <i>behind</i> shocks well known. We show that a Biermann-effect field also generated <i>within</i> shocks. Direct implementation MHD codes does not capture this physical process, worse, produces unphysical at whose value converge with resolution. convergence...
The relation of diffuse vibrational structures in UV-absorption spectra (small) polyatomic molecules and internal motion excited electronic states are investigated. method choice is the propagation time-dependent wavepackets with autocorrelation function serving as link between energy dependence spectrum time molecular state. For purpose this paper we characterize very short-lived resonances 'lifetimes' order at most one period. In particular, study a model system for photodissociation...
We investigate the photodissociation of CH3OH in first absorption band (S0→S1) by a two dimensional wave packet study employing associated internuclear potential energy surfaces obtained from ab initio calculations. The quantum chemical calculations are performed complete active space self-consistent field approach including CH3O and OH bond distances with CH3–O–H angle being fixed. methyl group is considered as structureless particle. nuclear functions ground excited electronic state then...
SUMMARY FLASH is a multiphysics multiscale adaptive mesh refinement (AMR) code originally designed for simulation of reactive flows often found in Astrophysics. With its wide user base and flexible applications configuration capability, has dual task maintaining scalability portability all solvers. The fully explicit solvers the tied very closely to that underlying mesh. Others such as Poisson solver based on multigrid method have more complex scaling behavior. Multigrid methods suffer from...