21,586 research outputs found

### A combined R-matrix eigenstate basis set and finite-differences propagation method for the time-dependent Schr\"{od}dinger equation: the one-electron case

In this work we present the theoretical framework for the solution of the
time-dependent Schr\"{o}dinger equation (TDSE) of atomic and molecular systems
under strong electromagnetic fields with the configuration space of the
electron's coordinates separated over two regions, that is regions $I$ and
$II$. In region $I$ the solution of the TDSE is obtained by an R-matrix basis
set representation of the time-dependent wavefunction. In region $II$ a grid
representation of the wavefunction is considered and propagation in space and
time is obtained through the finite-differences method. It appears this is the
first time a combination of basis set and grid methods has been put forward for
tackling multi-region time-dependent problems. In both regions, a high-order
explicit scheme is employed for the time propagation. While, in a purely
hydrogenic system no approximation is involved due to this separation, in
multi-electron systems the validity and the usefulness of the present method
relies on the basic assumption of R-matrix theory, namely that beyond a certain
distance (encompassing region $I$) a single ejected electron is distinguishable
from the other electrons of the multi-electron system and evolves there (region
II) effectively as a one-electron system. The method is developed in detail for
single active electron systems and applied to the exemplar case of the hydrogen
atom in an intense laser field.Comment: 13 pages, 6 figures, submitte

### High Voltage CMOS Control Interface for Astronomy - Grade Charged Coupled Devices

The Pan-STARRS telescope consists of an array of smaller mirrors viewed by a
Gigapixel arrays of CCDs. These focal planes employ Orthogonal Transfer CCDs
(OTCCDs) to allow on-chip image stabilization. Each OTCCD has advanced logic
features that are controlled externally. A CMOS Interface Device for High
Voltage has been developed to provide the appropiate voltage signal levels from
a readout and control system designated STARGRASP. OTCCD chip output levels
range from -3.3V to 16.7V, with two different output drive strenghts required
depending on load capacitance (50pF and 1000pF), with 24mA of drive and a rise
time on the order of 100ns. Additional testing ADC structures have been
included in this chip to evaluate future functional additions for a next
version of the chip.Comment: 13 pages, 17 gigure

### Comparison of numerical methods for the calculation of cold atom collisions

Three different numerical techniques for solving a coupled channel
Schroedinger equation are compared. This benchmark equation, which describes
the collision between two ultracold atoms, consists of two channels, each
containing the same diagonal Lennard-Jones potential, one of positive and the
other of negative energy. The coupling potential is of an exponential form. The
methods are i) a recently developed spectral type integral equation method
based on Chebyshev expansions, ii) a finite element expansion, and iii) a
combination of an improved Numerov finite difference method and a Gordon
method. The computing time and the accuracy of the resulting phase shift is
found to be comparable for methods i) and ii), achieving an accuracy of ten
significant figures with a double precision calculation. Method iii) achieves
seven significant figures. The scattering length and effective range are also
obtained.Comment: 22 pages, 3 figures, submitted to J. Comput. Phys. documentstyle
[thmsa,sw20aip]{article} in .te

### Electrical conductivity of chondritic meteorites

The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C

### R-matrix Floquet theory for laser-assisted electron-atom scattering

A new version of the R-matrix Floquet theory for laser-assisted electron-atom
scattering is presented. The theory is non-perturbative and applicable to a
non-relativistic many-electron atom or ion in a homogeneous linearly polarized
field. It is based on the use of channel functions built from field-dressed
target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

### Large-scale Breit-Pauli R-matrix calculations for transition probabilities of Fe V

Ab initio theoretical calculations are reported for the electric (E1) dipole
allowed and intercombination fine structure transitions in Fe V using the
Breit-Pauli R-matrix (BPRM) method. We obtain 3865 bound fine structure levels
of Fe V and $1.46 x 10^6$ oscillator strengths, Einstein A-coefficients and
line strengths. In addition to the relativistic effects, the intermediate
coupling calculations include extensive electron correlation effects that
represent the complex configuration interaction (CI). Fe V bound levels are
obtained with angular and spin symmetries $SL\pi$ and $J\pi$ of the (e + Fe VI)
system such that $2S+1$ = 5,3,1, $L \leq$ 10, $J \leq 8$. The bound levels are
obtained as solutions of the Breit-Pauli (e + ion) Hamiltonian for each $J\pi$,
and are designated according to the `collision' channel quantum numbers. A
major task has been the identification of these large number of bound fine
structure levels in terms of standard spectroscopic designations. A new scheme,
based on the analysis of quantum defects and channel wavefunctions, has been
developed. The identification scheme aims particularly to determine the
completeness of the results in terms of all possible bound levels for
applications to analysis of experimental measurements and plasma modeling. An
uncertainty of 10-20% for most transitions is estimated.Comment: 31 pages, 1 figure, Physica Scripta (in press

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### Charting new territory for organizational ethnography : Insights from a team-based video ethnography

Purpose: Increasing complexity, fragmentation, mobility, pace, and technological intermediation of organizational life make âbeing thereâ increasingly difficult. Where do ethnographers have to be, when, for how long, and with whom to âbe thereâ and grasp the practices, norms, and values that make the situation meaningful to natives? These novel complexities call for new forms of organizational ethnography. The purpose of this paper is to discuss the above issues.
Design/methodology/approach: In this paper, the authors respond to these calls for innovative ethnographic methods in two ways. First, the paper reports on the practices and ethnographic experiences of conducting a year-long team-based video ethnography of reinsurance trading in London.
Findings: Second, drawing on these experiences, the paper proposes a framework for systematizing new approaches to organizational ethnography and visualizing the ways in which they are âexpandingâ ethnography as it was traditionally practiced.
Originality/value: The paper contributes to the ethnographic literature in three ways: first, the paper develops a framework for charting new approaches to ethnography and highlight its different dimensions â site, instrument, and fieldworker. Second, the paper outlines the opportunities and challenges associated with these expansions, specifically with regard to research design, analytical rigour, and communication of results. Third, drawing on the previous two contributions, the paper highlights configurations of methodological expansions on the aforementioned dimensions that are more promising than others in leveraging new technologies and approaches to claim new territory for organizational ethnography and enhance its relevance for understanding today's multifarious organizational realities

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### Beyond Borders: Charting the Changing Global Reinsurance Landscape

This report is the result of a three-year study of the global reinsurance industry, covering the main stakeholders of cedents, reinsurers, and brokers. It examines the implications of profound change arising from shifts in regulation, consolidation in the key players, and increasing competition both within the reinsurance industry and from alternative capital providers. These changes are driving convergence in a market that was, until recently, characterised by significant cultural variation in buying and selling reinsurance. The findings in this report will help industry participants to take stock of their current position in the industry, the specific types of differentiation available, and how these differentiators can create advantage. Specifically, the report provides evidence-based frameworks and models that firms can use to diagnose their existing strategies and structures and consider alternatives

### Ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV above threshold

We present here triple differential cross sections for ionization of hydrogen
atoms by electron impact at 1eV, 0.5eV and 0.3eV energy above threshold,
calculated in the hyperspherical partial wave theory. The results are in very
good agreement with the available semiclassical results of Deb and Crothers
\cite{DC02} for these energies. With this, we are able to demonstrate that the
hyperspherical partial wave theory yields good cross sections from 30 eV
\cite{DPC03} down to near threshold for equal energy sharing kinematics.Comment: 6 pages, 9 figure

### Ionization potentials in the limit of large atomic number

By extrapolating the energies of non-relativistic atoms and their ions with
up to 3000 electrons within Kohn-Sham density functional theory, we find that
the ionization potential remains finite and increases across a row, even as
$Z\rightarrow\infty$. The local density approximation becomes chemically
accurate (and possibly exact) in some cases. Extended Thomas-Fermi theory
matches the shell-average of both the ionization potential and density change.
Exact results are given in the limit of weak electron-electron repulsion.Comment: 4 pages, 5 figure

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