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ICPEAC XX: A Retro- and Pro-Spective Analysis

Description: There is something magical about ``round birthdays.`` They make one stop and think about where he is, how he got there, and where he is going. The same is apparently true of conferences, especially those like ICPEAC which represent the periodic coming together of a broad range of scientists in a reasonably well-defined discipline. This Vienna conference is the 20th in the ICPEAC series, and a retro- and pro-spective analysis seems appropriate. At the first ICPEAC in New York (1958), there were about 50 participants. In Vienna (1997), there were more than 800 participants. How do we account for this growth? ICPEAC is one of the most democratic conferences of its size. For example, input from a general committee of 50 representing the many geographic and sub- disciplinary areas gives continuous refreshment of ideas for the invited program. And, as in any democracy, there is a constant state of turmoil and self doubt. After all, atomic collisions is a ``mature`` field, and was a ``mature`` field at the time of the first ICPEAC in 1958, 50 what can one expect in new developments? This self doubt is best expressed in the comment of Ben Bederson (the ``Father of ICPEAC``) following the second in Boulder, Colorado, in 1961: ``This conference is the second in a series of informal meetings organized by a group of workers in the general field of electronic and atomic collisions. The first such meeting was held at New York University in 1958, and we will probably continue to meet at irregular intervals in the future....`` As part of my ``keynote`` talk at the New York ICPEAC XVI in 1989, I gave a brief history of the conference which we can build on to round things off for our twentieth.
Date: December 31, 1997
Creator: Datz, S.
Partner: UNT Libraries Government Documents Department

Theoretical atomic collision physics. Final report, July 1, 1987-- June 30, 1995

Description: This is the final report of research activities supported by the most recent grant to the theoretical atomic collision physics program at Rice University. For this most recent 3-year grant, the focus has been the study of excitation and charge-transfer in atom-atom and ion-atom collisions. Emphasis has been placed on low-velocity collision processes involving initially excited atoms, including ``low Rydberg`` atoms. Two particular objectives of this research were to examine the dependence of state-changing collision cross sections and other observables on the orientation and alignment of the initial excited orbitals and to look for ``intracollisional interference`` effects, speculated to arise from spatially separated interactions during a collision involving a highly excited atom. A number of radiative and non-radiative charge transfer studies involving ground-state atoms and ions were continued from the previous grant period. Several unanticipated personnel changes prevented execution of some of the proposed research, including the studies of collisions involving negative ions and electron-attaching atoms and the development of new theoretical techniques for handling the ``strong coupling`` regime. These remain challenging and fundamentally important research topics. Research highlights briefly described in the report deal with: spherical and non-spherical low-Rydberg atom collisions; alignment effects in collisions of Na(3p) with He{sup +} ions; near-resonant electron capture at very low energies; ion-atom and ion-molecule collisions, including electron capture; and low- energy processes involving collisions of H{sup +} with He, Na, and K atoms. The report also lists publications since 1991 reporting on the grant work.
Date: December 1, 1995
Creator: Walters, G.K.
Partner: UNT Libraries Government Documents Department

Theory of Ionization by Electron Collisions

Description: The problem of calculating comprehensive sets of cross sections for ionization of atoms and molecules is reviewed. Emphasis is put on targets that are already ionized and lower-energy collisions for which the incident electron must be treated on a par with target electrons. The physical circumstances are discussed in which perturbation methods should be adequate, and special investigations are recommended to identify the relevant ranges of parameters more precisely and dependably. A new R-matrix approach is outlined which should permit rather simple, approximate, but dependable calculations when the perturbation methods fail.
Date: June 1976
Creator: Fano, Ugo & Inokuti, Mitio
Partner: UNT Libraries Government Documents Department

Proceedings of the Workshop on Electronic and Ionic Collision Cross Sections Needed in the Modeling of Radiation Interactions with Matter, Held at Argonne National Laboratory December 6-8, 1983

Description: The term modeling in the Workship title refers to the mathematical analysis of the consequences of many collision processes for characterizing the physical stage of radiation actions. It requires as input some knowledge of collision cross sections. Traditionally, work on cross sections and work on the modeling are conducted by separate groups of scientists. It was the purpose of the Workshop to bring these two groups together in a forum that would promote effective communication. Cross-section workers described the status of their work and told what data were available or trustworthy. Modeling workers told what kind of data were needed or were most important. Twenty-two items from the workshop were prepared separately for the data base.
Date: May 1984
Creator: Argonne National Laboratory
Partner: UNT Libraries Government Documents Department

Measurement of the Transverse Spitzer Resistivity during Collisional Magnetic Reconnection

Description: Measurement of the transverse resistivity was carried out in a reconnecting current sheet where the mean free path for the Coulomb collision is smaller than the thickness of the sheet. In a collisional neutral sheet without a guide field, the transverse resistivity is directly related to the reconnection rate. A remarkable agreement is found between the measured resistivity and the classical value derived by L. Spitzer. In his calculation the transverse resistivity for the electrons is higher than the parallel resistivity by a factor of 1.96. The measured values have verified this theory to within 30% errors.
Date: September 18, 2000
Creator: Trintchouk, F.; Yamada, M.; Ji, H.; Kulsrud, R.M. & Carter, T.A.
Partner: UNT Libraries Government Documents Department

Acceleration and collision of ultra-high energy particles using crystal channels

Description: We assume that, independent of any near-term discoveries, the continuing goal of experimental high-energy physics (HEP) will be to achieve ultra-high center-of-mass energies early in the next century. To progress to these energies in such a brief span of time will require a radical change in accelerator and collider technology. We review some of our recent theoretical work on high-gradient acceleration of charged particles along crystal channels and the possibility of colliding them in these same strong-focusing atomic channels. An improved understanding of energy and emittance limitations in natural crystal accelerators leads to the suggestion that specially manufactured nano-accelerators may someday enable us to accelerate particles beyond 10{sup 8} eV with emittances limited only by the uncertainty principle of quantum mechanics.
Date: April 1, 1997
Creator: Chen, P. & Noble, R.J.
Partner: UNT Libraries Government Documents Department

Ion-Molecule Reactions

Description: Introduction: The present report is a critical review of the present knowledge and theory of ion-molecule reactions, especially as they may apply to high-level radiation processing.
Date: October 1959
Creator: Rosenstock, H. M.; Mueller, C. R.; Wallenstein, M. B.; Vestal, Marvin L.; Tory, Audrey; Rivers, Diana et al.
Partner: UNT Libraries Government Documents Department

Few electron transitions in atomic collisions. Final report, September 1, 1992--December 31, 1995

Description: During the past three years we have evaluated probabilities and cross sections for few and multiple electron transitions in atomic collisions. Our studies included interactions of atoms and molecules with incident protons, bare ions, electrons, positrons, anti-protons, ions carrying electrons and photons. We also: studied the inter-relation between collisions with charged particles and collisions involving various processes with photons. This work has complemented various studies of collisions of atoms with charged particles and with photons as well as more general efforts to understand the nature of multi-electron systems. Our aim has been to begin with relatively simple two electron systems and to focus on fast processes in which there is too little time for complicated processes to occur. We have used a variety of computational techniques, but we emphasize those appropriate for fast collisions in which we hope to obtain insight into the physical nature of the process itself. We generally considered systems in which experimental data was available.
Date: April 1, 1997
Creator: McGuire, J.
Partner: UNT Libraries Government Documents Department

Measurement of x-rays emitted from projectiles moving in solid targets

Description: The results of three separate experiments all dealing with the production of x-rays in projectiles moving in solids are discussed. The first experiment deals with the measurement of line widths of x-rays emitted from projectiles moving in solid targets. The effect of collisional broadening of x- rays is found to dominate the line widths giving greater than an order of magnitude increase in the measured line widths. The second experiment studies ''solid target effects'' in producing non-binomial distributions of characteristic K x-ray spectra in heavy ion-atom collisions. The third experiment studies aluminum K x-ray production in Ar$sup +$ $Yields$ Al collisions in very thin aluminum foils as a function of foil thickness. Parameterization of the observed non-linear dependence enables the lifetime of the argon 2p vacancy and total ionization cross sections for the argon L-shell in Ar $Yields$ Al collisions to be measured. (auth)
Date: January 1, 1975
Creator: Fortner, R.J.; Matthews, D.L.; Feldman, L.C.; Garcia, J.D. & Oona, H.
Partner: UNT Libraries Government Documents Department

Backscattering of light ions from metal surfaces

Description: When a metal target is bombarded with light ions some are implanted and some are reflected from the surface or backscattered from deeper layers. This results in an energy distribution of the backscattered particles which reaches from zero to almost the primary energy. The number of the backscattered particles and their energy, angular, and charge distributions depends largely on the energy and the ion target combination. For high energies (i.e., greater than50 keV for protons) particles are backscattered in a single collision governed by the Rutherford cross section. Protons and He-ions with energies of 100 keV to several MeV are widely used for thin film analysis. For lower energies multiple collisions and the screening of the Coulomb potential have to be taken into account, which makes the theoretical treatment more difficult. This energy region is, however, of special interest in the field of nuclear fusion research. Some recent results for energies below 20 keV are discussed in some detail. (auth)
Date: July 1, 1975
Creator: Verbeek, H.
Partner: UNT Libraries Government Documents Department

A Vehicle-collision Learning System Using Driving Patterns on the Road

Description: Demand of automobiles are significantly growing despite various factors, steadily increasing the average number of vehicles on the road. Increase in the number of vehicles, subsequently increases the risk of collisions, characterized by the driving behavior. Driving behavior is influenced by factors like class of vehicle, road condition and vehicle maneuvering by the driver. Rapidly growing mobile technology and use of smartphones embedded with in-built sensors, provides scope of constant development of assistance systems considering the safety of the driver by integrating with the information obtained from the vehicle on-board sensors. Our research aims at learning a vehicle system comprising of vehicle, human and road by employing driving patterns obtained from the sensor data to develop better systems of safety and alerts altogether. The thesis focusses on utilizing together various data recorded by the in-built embedded sensors in a smartphone to understand the vehicle motion and dynamics, followed by studying various impacts of collision events, types and signatures which can potentially be integrated in a prototype framework to detect variations, alert drivers and emergency responders in an event of collision.
Date: August 2013
Creator: Urs, Chaitra Vijaygopalraj
Partner: UNT Libraries

Ultra-cold molecule production.

Description: The production of Ultra-cold molecules is a goal of many laboratories through out the world. Here we are pursuing a unique technique that utilizes the kinematics of atomic and molecular collisions to achieve the goal of producing substantial numbers of sub Kelvin molecules confined in a trap. Here a trap is defined as an apparatus that spatially localizes, in a known location in the laboratory, a sample of molecules whose temperature is below one degree absolute Kelvin. Further, the storage time for the molecules must be sufficient to measure and possibly further cool the molecules. We utilize a technique unique to Sandia to form cold molecules from near mass degenerate collisions between atoms and molecules. This report describes the progress we have made using this novel technique and the further progress towards trapping molecules we have cooled.
Date: December 1, 2005
Creator: Ramirez-Serrano, Jamie; Chandler, David W.; Strecker, Kevin & Rahn, Larry A.
Partner: UNT Libraries Government Documents Department

Excitation states of projectiles moving through solids

Description: From 3rd international conference on atomic collisions in solids; Gatlinburg, Tennessee, USA (23 Sep 1973). X-ray spectral measurements of S, Cl, and Ar atoms moving in solid carbon targets are used to extract the equilibrium distribution of vacancies in the valence and L-shells of the projectiles. It is found that the state of excitation is much higher than the mean charge measured after the projectile has left the solid. A simple model is used to deduce the expected final charge state distribution, and these are compared to thin foil measurements. The results support the Betz-Grodzins model for ions moving in solids. (auth)
Date: September 1, 1973
Creator: Fortner, R.J. & Garcia, J.D.
Partner: UNT Libraries Government Documents Department

Comparison with European observations of meteor impact

Description: A model for the inference of object size and speed from observations is used to discuss European observations of impact. It compares the observed and predicted breakup altitudes for the objects larger than one meter and observes useful correlations. Trends in magnitude correlate well with measured velocities, altitudes, and trajectories and inferred size and strength parameters, but each parameter is subject to dispute, which can only be addressed when the sensitivity of predictions to uncertainties in these parameters is assessed.
Date: June 1, 1997
Creator: Canavan, G. H.
Partner: UNT Libraries Government Documents Department

SciDAC - Center for Plasma Edge Simulation - General Atomics Support of NYU Collaborations

Description: Methods for implementing Coulomb collisions in particle codes were studied and developed. At first, a lattice-Boltzmann method seemed promising. After considering this in more detail, it was found not to be efficient enough. A method was then sought for implementing collisional effects as changes in particle weights, instead of changes in velocities. Although this may eventually be done, it was decided that a Langevin method would be more straightforward to develop, since it was possible to build on previous work. The rest of the contract period was spent developing the Langevin method, which ultimately resulted in a published paper, in April 2008 [F.L. Hinton, Phys. Plasma 15, 042501 (2008)].
Date: June 30, 2009
Creator: Hinton, F.L. & Staff, Project
Partner: UNT Libraries Government Documents Department

On the quantum mechanical theory of collisional recombination rates, II. Beyond the strong collision approximation

Description: A quantum mechanical theory of collisional recombination (within the Lindemann mechanism, A + B {leftrightarrow} AB*, AB* + M {yields} AB + M) is presented which provides a proper quantum description of the A + B collision dynamics and treats the M + AB* inelastic scattering within the impact approximation (the quantum analog of a classical master equation treatment). The most rigorous version of the theory is similar in structure to the impact theory of spectral line broadening and involves generalized (4-index) rate constants for describing M + AB* collisions. A simplified version is also presented which involves only the normal (2-index) inelastic rate constants for M + AB* scattering but which also retains a proper quantum description of the A + B dynamics.
Date: July 1, 1995
Creator: Miller, W.H.
Partner: UNT Libraries Government Documents Department

Three-body collision contributions to recombination and collision-induced dissociation. 1: Cross sections

Description: Atomic and molecular recombination and collision-induced dissociation (CID) reactions comprise two of the most fundamental types of chemical reactions. They are important in all gas phase chemistry; for example, about half of the 196 reactions identified as important in combustion chemistry are recombination or CID reactions. Many of the current chemical kinetics textbooks and kinetics papers treat atomic and molecular recombination and CID as occurring only via sequences of two-body collisions. Actually, there is considerable evidence from experiment and classical trajectory calculations for contributions by true three-body collisions to the recombination of atomic and diatomic radicals, and that evidence is reviewed. Then, an approximate quantum method treating both two-body and three-body collisions simultaneously and on equal footing is used to calculate cross sections for the reaction Ne{sub 2} + H {rightleftharpoons} Ne + Ne + H. The results provide clear quantum evidence that direct three-body collisions do contribute significantly to recombination and CID.
Date: April 10, 1998
Creator: Pack, R. T.; Walker, R. B. & Kendrick, B. K.
Partner: UNT Libraries Government Documents Department

Theory and modeling in combustion chemistry

Description: This paper discusses four important problems in combustion chemistry. In each case, resolution of the problem focuses on a single elementary reaction. Theoretical analysis of this reaction is discussed in some depth, with emphasis on its unusual features. The four combustion problems and their elementary reactions are: (1) Burning velocities, extinction limits, and flammability limits: H+O{sub 2}{leftrightarrow}OH+O, (2) Prompt NO: CH+N{sub 2}{leftrightarrow}HCN+N, (3) the Thermal De-NO{sub x} Process: NH{sub 2}+NO{leftrightarrow}products, and (4) ``Ring`` formation in flames of aliphatic fuels and the importance of resonantly stabilized free radicals: C{sub 3}H{sub 3}{leftrightarrow}products.
Date: October 1, 1996
Creator: Miller, J.A.
Partner: UNT Libraries Government Documents Department