Browsing by Author "Lane, Neal F."
Now showing 1 - 20 of 33
Results Per Page
Sort Options
Item A study of local exchange in continuum processes(1980) O'Connell, James Kevin; Lane, Neal F.; Walters, G. King; Huang, Huey W.The role of one electron orbitals in Many Body Theory and the Generalized Sudden Approximation is reviewed. Various approximations to the exact Hartree Fock static exchange potentials are discussed and a new, screened exchange potential is derived. Phase shifts for the elastic scattering of electrons from Helium, Neon and Argon and Photoionization cross sections for Lithium, Carbon, Oxygen, Neon and Argon were calculated and compared with the exact static exchange results. The screened exchange potential is the best approximation for Photoionization and the Hara exchange potential is the best for Scattering. Ground state eigenvalues, ionization energies and oscillator strengths have been calculated for the 2t2-la1 transition in Methane. The calculations were carried out using the Xalpha Multiple Scattering Method. The ground state eigenvalues were correctly predicted and the oscillator strengths lie within experimental limits.Item Adiabetic electric field ionization of Sodium Rydberg atoms(1982) McMillian, Gary Benton; Stebbings, Ronald F.; Dunning, F. Barry; Lane, Neal F.Utilizing the technique of high resolution selective field ionization it is possible to observe ionization structure as narrow as 2 V/cm for Na(nS,nD) atoms. Field ionization structure this narrow is characteristic of atoms evolving predominantly adiabatically in a rapidly increasing electric field. By increasing the slew rate of the applied field it is possible to induce departures from the adiabatic path at specific avoided level crossings. These departures result in multiple ionization thresholds which may be explained by arguments based on a simple quantum mechanical model of adiabatic field ionization.Item An expansion of the s-wave low energy electron-heavy noble gas atom scattering cross sections about a virtual state and a study of the associated Ramsauer-Townsend effect(1972) Cook, Thomas Leroy; Lane, Neal F.In this paper the Ramsauer-Townsend effect is investigated for the rare gases Ar, Kr, and Xe. The usual modified effective range formulae for electron-atom scattering are replaced by an expansion of the s-wave phase shifts about a low-lying virtual state. A critical review of the experimental work which has been performed on the above systems for low energy total elastic electronatom scattering cross sections and for momentum-transfer cross sections is included.Item Basis representations for atomic collision problems: application to He_ + He*, _[Sigma]+g, two-state calculation(1970) Cohen, James Samuel; Lane, Neal F.The coupled equations for the heavy-particle motion in atomic collisions are reviewed with emphasis on the transformation of the equations between different basis representations, in particular the adiabatic and diabatic representations. The application to the two-state approximation neglecting angular coupling is made and the required matrix elements and methods of evaluating these matrix elements are discussed; the various coupling terms are examined. Elastic and inelastic transition cross sections are calculated for collisions between metastable helium, He(1s2s,3S), and ground state helium. The inelastic transition He(1s28,3S) ---> He(1s2p0,3P) can occur in this collision due to the avoided crossing of the lowest two adiabatic 3 sigma, ^ +g potential curves for He2. The close coupling results are compared to results obtained using the adiabatic and diabatic decoupling approximations and the distorted wave approximation.Item Bridging the Gap Between Science and Society: The Relationship Between Policy and Research in National Laboratories, Universities, Government, and Industry(2006) Matthews, Kirstin R.W.; Lane, Neal F.; Jaffe, Amy Myers; Bierbaum, Rosina; James A. Baker III Institute for Public PolicyItem Classical study of collisions of Rydberg atoms with polar molecules(1982) Preston, Steven Craig; Lane, Neal F.; Trammell, George T.; Stebbings, Ronald F.Cross sections for state changing collisions of Rydberg atoms with polar molecules have been calculated using a classical trajectory Monte-Carlo technique. Although the dynamical problem was restricted to two dimensions, useful insights into the full three dimensional system were obtained. For example it was found that at thermal velocities the Rydberg electron can collide with the molecule many times during a angle trajectory. This implies that the impulse approximation, which is commonly used for many Rydberg collision problems, is not valid for this problem, since it cannot account for this effect. Finally, a finite effective range for the dipole interaction was observed, which can be used to make the calculation of three dimensional cross sections more tractable. Without these insights, the three dimensional calculation would have been much more difficult and costly.Item Conference Report—Beyond Science: The Economics and Politics of Responding to Climate Change(2008) Matthews, Kirstin R.W.; Smulcer, Lauren A.; Jaffe, Amy Myers; Lane, Neal F.; James A. Baker III Institute for Public PolicyTo examine climate change issues from a policy and scientific perspective, the Science and Technology Policy, Energy Forum, and Health Economics programs of the James A. Baker III Institute for Public Policy, together with the Energy & Environmental Systems Institute and the Shell Center for Sustainability at Rice University, hosted a conference on February 9, 2008, titled “Beyond Science: The Economics and Politics of Responding to Climate Change.” The event, supported by the Science & Innovation Section of the British Consulate-General in Houston, sought to highlight the challenges and opportunities for developing a more effective U.S. climate policy. Conference participants discussed policies that have been adopted or are under consideration in the United States, as well as the background data needed to assess the effectiveness of these policies and other options. Among the topics covered were the Intergovernmental Panel on Climate Change (IPCC) 2007 Assessment Report; mitigation and adaptation strategies; policy approaches to limiting carbon emissions and the economic issues related to such policies; and technology options for dealing with climate change. This conference report is a summary of the findings and discussions.Item Congressional Briefing for United States Space Policy: Challenges and Opportunities Gone Astray(James A. Baker III Institute for Public Policy, 2009) Abbey, George W.S.; Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Considering Sea Level Rise(James A. Baker III Institute for Public Policy, 2008) Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Differential change exchange cross sections for collisions of HE++ ions with H atoms(1983) Day, Amelia; Lane, Neal F.; Stebbings, Ronald F.; Chamberlain, Joseph W.Differential charge exchange cross sections are presented for ^4He^++ incident on an H(ls) atom for projectile energies of 3, 8, and 2 keV. A molecular state basis and straight line impact parameter formalism are used in the semiclassical eikonal approximation. Calculations were made with a ten state basis modified by Bates and McCarroll plane-wave translational factors and with an unmodified four state basis. Only cross sections corresponding to electron transfer into He+ (n = 2) states are included. Large and small angle oscillations are examined in terms of a diffractive scattering process. These results are consistent with other theoretical calculations.Item Hot Topic: Navigating the Fact and Fiction of Climate Change(James A. Baker III Institute for Public Policy, 2007) Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Hot Topic: Stem Cell Controversy: Are Human Skin Cells Really the Breakthrough?(James A. Baker III Institute for Public Policy, 2007) Matthews, Kirstin R.W.; Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Hot Topic: Stem Cell Controversy: Are Human Skin Cells Really the Breakthrough?(James A. Baker III Institute for Public Policy, 12/7/2007) Lane, Neal F.; Matthews, Kirstin R.W.; James A. Baker III Institute for Public PolicyItem Human Embryonic Stem Cell Research: Recommendations for the Next Administration(2008) Matthews, Kirstin R.W.; Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Hydrogen in metals: screening, resistivity, and diffusion(1975) Shaw, Milton Samuel; Lane, Neal F.The theory of screening of a potential in various approximations of a metal are reviewed. Phase shifts were calculated for free electron scattering by a Yukawa potential, and the screening parameter was adjusted to satisfy the Friedel sum rule. Using these phase shifts, residual resistivities of hydrogen in various metals were calculated in qualitative agreement with experiment. The theories of diffusion of hydrogen in metals are reviewed. A model for the hydrogenmetal interaction has been constructed using linear response screening for the hydrogen and superposition of neutral atoms for the metal. Screening in the region of the metal cores was treated with a pseudopotential. The occupation of octahedral sites in FCC metals and tetrahedral sites in BCC metals is correctly predicted. Vibrational energy level spacing for Pd and Ni were calculated to be .8 eV and .16 eV, respectively. Experimental values are .6 eV and .12 eV. Activation energies for diffusion are estimated with qualitative agreement with experiment.Item Nuclear Nonproliferation: Policy Implications(2007) Abbey, George W.S.; Lane, Neal F.; James A. Baker III Institute for Public PolicyItem Nuclear Nonproliferation: Policy Implications(11/2/2007) Lane, Neal F.; Abbey, George W.S.; James A. Baker III Institute for Public PolicyItem On the interaction of metastable hydrogen and helium atoms with a metal surface(1975) Carlson, Lawrence Walter; Lane, Neal F.A theoretical study of the adiabatic interaction of a metastable 2s hydrogen (or 2^1,3 S helium) atom with an idealized metal surface has been carried out where account has been taken of the 2s-2p state mixing due to the atom metal interaction. The variationally determined wavefunction and resonant-ionization rate are calculated as a function of atom-surface separation. It is found for the 2s(2p) state that the 2s-2p mixing causes a substantial lowering (raising) of the electronic energy and an increase (decrease) in the ionization rate. The competitive process of Penning ionization of adsorbed atoms is discussed using a simple model.Item Pseudopotential studies of e-H¿ collisions(1978) Haggard, J. Alan; Lane, Neal F.Developments in the theory of electron scattering from molecules are delineated with the pseudopotential studies presented as an outgrowth of these undertakings. The coupled equations are educed in the pseudopotential framework, and elastic s-wave solutions are obtained without coupling of partial waves. A numerically simpler, though similar, treatment is presented and utilized to obtain results not too discrepant from those of the pseudopotentials. It is concluded that the approach is propitious but extensions of it should include the effects of partial wave coupling.Item Radiative charge transfer in collisions of He++ ions with H(1s) atoms(1982) West, Benjamin William; Lane, Neal F.; Dunning, F. Barry; Huang, Huey W.Total cross sections for radiative charge transfer during collisions of He ions with H(ls) atoms leading to He+(ls) and H+ ions have been calculated at center of mass energies ranging from .1 to 1 eV. Since it is known from coupled-states calculations that non-adiabatic coupling effects are small at these energies, the problem is formulated in the adiabatic approximation where the 2pa molecular state is represented by an optical model potential. In this treatment, the radiative decay of the 2pa state of the HeH++ molecule is described by the imaginary part of the optical potential, which incorporates the 2pa - Isa transition rate (Einstein A coefficient). This transition rate for fixed intemuclear separations was calculated using ab initio wavefunctions of the HeH++ molecule For energies in the range where penetration of the centrifugal barrier is unimportant (E ^ 1 eV), cross sections were estimated via the JWKB approximation. At lower energies, the effect of tunneling is more important, and resonances associated with the predissociating states of the HeH++ molecule will dominate the structure in the cross sections. At these energies, cross sections are calculated by integrating the radial equation using the Numerov algorithm. The calculated cross sections vary from 4x1 cm at .1 eV to 1.4x1 cm at 1 eV. The radiative contribution to the total charge transfer cross section probably dominates at energies below 5 eV.