112,606 research outputs found
Excitation energies, polarizabilities, multipole transition rates, and lifetimes of ions along the francium isoelectronic sequence
Relativistic many-body perturbation theory is applied to study properties of
ions of the francium isoelectronic sequence. Specifically, energies of the 7s,
7p, 6d, and 5f states of Fr-like ions with nuclear charges Z = 87 - 100 are
calculated through third order; reduced matrix elements, oscillator strengths,
transition rates, and lifetimes are determined for 7s - 7p, 7p - 6d, and 6d -
5f electric-dipole transitions; and 7s - 6d, 7s - 5f, and 5f_5/2 - 5f_7/2
multipole matrix elements are evaluated to obtain the lifetimes of low-lying
excited states. Moreover, for the ions Z = 87 - 92 calculations are also
carried out using the relativistic all-order single-double method, in which
single and double excitations of Dirac-Fock wave functions are included to all
orders in perturbation theory. With the aid of the SD wave functions, we obtain
accurate values of energies, transition rates, oscillator strengths, and the
lifetimes of these six ions. Ground state scalar polarizabilities in Fr I, Ra
II, Ac III, and Th IV are calculated using relativistic third-order and
all-order methods. Ground state scalar polarizabilities for other Fr-like ions
are calculated using a relativistic second-order method. These calculations
provide a theoretical benchmark for comparison with experiment and theory.Comment: 13 figures, 11 table
Excitation energies, polarizabilities, multipole transition rates, and lifetimes in Th IV
Excitation energies of the ns_{1/2} (n=7-10), np_j (n=7-9), nd_j (n=6-8),
nf_{j} (n=5-7), and ng_{j} (n=5-6) states in Th IV are evaluated. First-,
second-, third-, and all-order Coulomb energies and first- and second-order
Coulomb-Breit energies are calculated. Reduced matrix elements, oscillator
strengths, transition rates, and lifetimes are determined for the 96 possible
nl_j-n'l'_j' electric-dipole transitions. Multipole matrix elements
(7s_{1/2}-6d_j, 7s_{1/2}-5f_j, and 5f_{5/2}-5f_{7/2}) are evaluated to obtain
the lifetimes of the and 7s_{1/2}$ states. Matrix elements are
calculated using both relativistic many-body perturbation theory, complete
through third order, and a relativistic all-order method restricted to single
and double (SD) excitations. Scalar and tensor polarizabilities for the
5f_{5/2} ground state in Th3+ are calculated using relativistic third-order and
all-order methods. These calculations provide a theoretical benchmark for
comparison with experiment and theory.Comment: 9 pages, 9 figure
Submerged gas injector expels cryogenic liquids from tanks
Vaporizing small portion of cryogenic liquid into pressurizing gas reduces amount of pressurizing gas required to expel cryogenic liquid from tank. Specific example of injecting helium gas, stored at same temperature of liquid hydrogen, through submerged porous plate directly into liquid hydrogen is described
Microwave switching power divider
A pair of parallel, spaced-apart circular ground planes define a microwave cavity with multi-port microwave power distributing switching circuitry formed on opposite sides of a thin circular dielectric substrate disposed between the ground planes. The power distributing circuitry includes a conductive disk located at the center of the substrate and connected to a source of microwave energy. A high speed, low insertion loss switching diode and a dc blocking capacitor are connected in series between the outer end of a transmission line and an output port. A high impedance, microwave blocking dc bias choke is connected between each switching diode and a source of switching current. The switching source forward biases the diodes to couple microwave energy from the conductive disk to selected output ports and, to associated antenna elements connected to the output ports to form a synthesized antenna pattern
Multispectral analysis of ocean dumped materials
Experiments conducted in the Atlantic coastal zone indicated that plumes resulting from ocean dumping of acid wastes and sewage sludge have unique spectral characteristics. Remotely sensed wide area synoptic coverage provided information on these pollution features that was not readily available from other sources. Aircraft remotely sensed photographic and multispectral scanner data were interpreted by two methods. First, qualitative analyses in which pollution features were located, mapped, and identified without concurrent sea truth and, second, quantitative analyses in which concurrently collected sea truth was used to calibrate the remotely sensed data and to determine quantitative distributions of one or more parameters in a plume
Quantitative suspended sediment mapping using aircraft remotely sensed multispectral data
Suspended sediment is an important environmental parameter for monitoring water quality, water movement, and land use. Quantitative suspended sediment determinations were made from analysis of aircraft remotely sensed multispectral digital data. A statistical analysis and derived regression equation were used to determine and plot quantitative suspended sediment concentration contours in the tidal James River, Virginia, on May 28, 1974. From the analysis, a single band, Band 8 (0.70-0.74 microns), was adequate for determining suspended sediment concentrations. A correlation coefficient of 0.89 was obtained with a mean inaccuracy of 23.5 percent for suspended sediment concentrations up to about 50 mg/l. Other water quality parameters - secchi disc depth and chlorophyll - also had high correlations with the remotely sensed data. Particle size distribution had only a fair correlation with the remotely sensed data
A planning logic for exploration and utilization of the moon
Planning logic for exploration and utilization of moo
Filtering techniques for noise suppression in quasi-balanced circuits
Filtering techniques for noise suppression in quasi-balanced circuit
Atmospheric effects on METSAT data
When using the J. V. Dave dataset, two channels of simulated METSAT advanced very high resolution radiometer (AVHRR) data compare favorably with actual data. Simulated NOAA6 and NOAA7 AVHRR data are presented as radiance profiles of reflected solar energy through atmosphere with three different aerosol levels. Effects of the atmosphere on the data are presented as functions of satellite view angle or pixel position on scanline. Vegetative index simultations are also profiled
Resin additive improves performance of high-temperature hydrocarbon lubricants
Paraffinic resins, in high temperature applications, improve strength of thin lubricant film in Hertzian contacts even though they do not increase bulk oil viscosity. Use of resin circumvents corrosivity and high volatility problems inherent with many chemical additives
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