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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Comparison of Trajectory Models in Calculations of N2-broadened Half-widths and N2-induced Line Shifts for the Rotational Band of H2O-16 and Comparison with Measurements

In this work, Complex Robert-Bonamy calculations of half-widths and line shifts were done for N2-broadening of water for 1639 transitions in the rotational band using two models for the trajectories. The first is a model correct to second order in time, the Robert-Bonamy parabolic approximation. The second is the solution of Hamilton's equations. Both models use the isotropic part of the atom-atom potential to determine the trajectories. The present calculations used an intermolecular potential expanded to 20th order to assure the convergence of the half-widths and line shifts. The aim of the study is to assess if the difference in the half-widths and line shifts determined from the two trajectory models is greater than the accuracy requirements of the spectroscopic and remote sensing communities. The results of the calculations are compared with measurements of the half-widths and line shifts. It is shown that the effects of the trajectory model greatly exceed the needs of current remote sensing measurements and that line shape parameters calculated using trajectories determined by solving Hamilton's equations agree better with measurement.

Lamouroux, J.↗
DOE OSTI2025

Alpha-decay width of a near proton-threshold resonance in the 7 Li( α, α ) channel

We investigate the alpha-decay width of a near proton-threshold resonance in 11 B by the excitation functions of 7 Li(α, α) and 7 Li(α, α’) reactions. This resonance is an example of loosely bound atomic nuclei, understood as small open quantum systems, that exhibit properties significantly influenced by their coupling to the continuum. The present experiment focuses on the formation of a specific state in 11 B at excitation energy in the region near 11.4 MeV by bombarding a 7 Li target with a 4 He beam at energies ranging from 3.92 to 4.56 MeV in the laboratory frame. The study provides data complementary to previous observations of the proton emission in the β-decay of the neutron-rich halo nucleus 11 Be. An R-matrix fit to the data provides resonance energy and partial widths consistent with J π =1/2 + for a narrow near-threshold state in 11 B at 11.400(20) MeV, that is 171(20) keV above the proton emission threshold, with partial α-decay width Γ α =2.5$^{+3.5}_{–1.5}$ keV in elastic scattering and Γ α' =15.8$^{+1.9}_{–0.4}$ keV in inelastic scattering. These findings contribute to the understanding of the structure of this open quantum system resonance.

11B↗
DOE OSTI2024

Transition width of the of the $J$ $π$ = $1$ – two-phonon state of $88$ $Sr$

The ground-state decay width of the two-phonon $J$ $π$ = $1$ – , 4742 keV state of 88 Sr has been determined with the relative self-absorption method combined with a monoenergetic photon beam. This width is important to determine the decay transition strengths into the ground state and the one-phonon $2$$^{+}_{1}$ and $3$$^{–}_{1}$ levels which are required to verify the two-phonon character of the $J$ $π$ = $1$ – state. Here, the experiment was performed at the High Intensity γ-ray Source (HI⁢ γ⁢S) using a novel experimental approach to adapt the relative self-absorption method to monoenergetic photon beams. The result for the ground-state decay width is, thus, independent of any calibration standard and confirms the two-phonon character of the 88 Sr, $J$ $π$ = $1$ – , 4742 keV state within an improved uncertainty.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1972

Shapes and widths of ammonia lines collision-broadened by hydrogen.

Measurement of half-widths and shapes of several rotational lines in nu sub 2 bands of ammonia, collision-broadened by hydrogen. The measurements were made at room temperature with a spectral resolution of 0.15 per cm. Line intensities and self-broadened half-widths were also measured. From the line-intensity data, an estimate of S sub band = 600 plus or minus 30 per sq cm per atm has been derived for the absolute intensity of the pair of bands. Hydrogen-broadened half-widths of all the lines have been found to be equal to 0.075 plus or minus 0.004 per cm per atm. For all the lines measured, shapes of the lines in NH3-H2 collisions seem to conform to the super-Lorenz line shape proposed by Varanasi et al. (1972) for dipole quadrupole collisions.

Varanasi, P.↗
NASA NTRS1973

Methane absorption in the Jovian atmosphere. I - The Lorentz half-width in the 3nu/sub 3/ band at 1.1 micron.

The Lorentz half-width alpha (L), of the fine-structure components of the methane 3nu/sub 3/ R-branch in the Jovian spectrum has been measured from photoelectric observations of the singlet R(1). Curves of growth for the 3nu/sub 3/ R-branch manifolds have been calculated, using the measured value of alpha (L) and assuming a reflecting-layer atmosphere. The Walker-Hayes (1967) equivalent widths have been reanalyzed for rotational temperature and methane abundance. The half-width derived here is significantly different from a similar measurement made by Farmer (1969). The source of the discrepancy remains obscure.

Bergstralh, J. T.↗
NASA NTRS1974

Effects of intrinsic region width in Si/Li/ p-i-n diodes

Description of certain effects related to the width of the intrinsic region produced in a silicon p-i-n diode by lithium ion drifting. It is found that for wider intrinsic regions at large forward biases there is a larger ohmic drop across the region and a correspondingly smaller current. Moreover, the recovery time decreases with increasing intrinsic region width. Conversely, the decay phase time increases with increasing intrinsic region width and with increasing current levels.

Harman, T. L.↗
NASA NTRS1975

Measurement of line widths of CO of planetary interest at low temperatures

Self-broadened, air-broadened and CO2-broadened half-widths of lines R(0) through R(16) in the CO fundamental have been measured at 100 K (self-broadening only), 200 K, 250 K and 300 K using the Ladenburg-Reiche curve-of-growth. The relation which we found previously for the nitrogen-broadened half-widths of R(0), R(8), and R(16), is shown to be valid for all of the line widths measured in the present study.

Varanasi, P.↗
NASA NTRS1975

Optically thick line widths in pyrotechnic flares

Experimentally determined sodium line widths for pyrotechnic flares are compared with simple analytical, optically-thick-line-shape calculations. Three ambient pressure levels are considered (760, 150 and 30 torr) for three different flare compositions. The measured line widths range from 1.3 to 481 A. The analytic procedure emphasizes the Lorentz line shape as observed under optically-thick conditions. Calculated widths are in good agreement with the measured values over the entire range.

Douda, B. E.↗
NASA NTRS1976

Shift and width measurements of the Stark-broadened ionized helium line at 1215 A

Time-resolved photoelectric measurements were made of the shifts of helium plasma lines at 1640 A and 1215 A and of the Stark profile of the 1215 A line, using an electromagnetic shock tube as a light source. These red shifts are consistent with a plasma polarization shift, where the interaction energy between the radiating ion and the perturbing plasma electrons corresponds to the Coulomb interaction near the excited state Bohr radius. No significant shifts were observed for the 1640 A line, while the 1215 A line underwent a red shift of about 0.5 A. The measured Stark width of the 1215 A line was 10-45% greater than the calculated width based on the measured width of the 4686 A line.

Van Zandt, J. R.↗
NASA NTRS1977

The influence of stripe width on the threshold current of double-heterojunction lasers

Experimental measurements of the threshold current of oxide-isolated stripe laser as a function of stripe width and p-layer resistivity are presented. A calculation of the influence of carrier outdiffusion has been made, including the effect of current leakage beyond the stripe edges. The calculated threshold increase is in substantial agreement with experiment for stripe widths down to about 10 microns. The data also yield an effective diffusion length of about 7 microns for the lasers studied. Deviations between experimental and calculated thresholds occurring at stripe widths of 4-6 microns are represented by an empirical curve which is compared with previously published calculations of threshold gain.

Ladany, I.↗
NASA NTRS1980

Active notch filter network with variable notch depth, width and frequency

An active notch filter having independently adjustable notch frequency, width, and depth is provided by three equal capacitors connected in series with an operational amplifier (connected in a voltage follower configuration), a potentiometer across the series connected capacitors for notch depth adjustment, and a potentiometer (for notch frequency connected across the center capacitor); with its tap connected to receive a voltage feedback signal from a variable voltage divider comprised of another potentiometer for notch width. Adjusting the voltage dividing potentiometer will independently set the notch width, and adjusting the tap on the potentiometer across the center capacitor will independently adjust the notch frequency of the filter. A second operational amplifier connected in a voltage follower configuration may be used to connect the voltage divider output to the adjustable tap of the potentiometer across the center capacitor.

Black, J. M.↗
NASA NTRS1981

Measurement of the oscillator strengths and autoionization widths of the neutral-aluminum multiplet 3s2 3p2 P0 - 3s 3p2 2P

The hook method is used in conjunction with absorption equivalent width measurements to determine the oscillator strengths and line widths of the Al I multiplet 3s2 3p2 P0 - 3s 3p2 2P at 176 nm. Autoionization is found to be the dominant decay channel for the two levels of the 3p2 2P term, with autoionizing widths of 4.0 and 0.87 x 10 to the 10th/sec for J of 3/2 and 1/2, respectively. The van der Waals scattering cross section for the Al I transition at 176.91 nm by He is determined to be (1.3 + or - 0.3) x 10 to the -14th sq cm at 2400 K, and a solar spectrum calculation centered at 176 nm shows that the Al I features are possible diagnostic probes of (1) solar non-LTE processes, and (2) the temperature minimum and structure of the lower chromosphere.

Lombardi, G. G.↗
NASA NTRS1982

Radial widths, optical depths, and eccentricities of the Uranian rings

Observations of the stellar occultation by the Uranian rings of 15/16 August 1980 are used to estimate radial widths and normal optical depths for segments of rings 6, 5, 4, alpha, beta, eta, gamma, and delta. Synthetic occultation profiles are generated to match the observed light curves. A review of published data confirms the existence of width-radius relations for rings alpha and beta, and indicates that the optical depths of these two rings vary inversely with their radial widths. Masses are obtained for rings alpha and beta, on the assumption that differential precession is prevented by their self-gravity. A quantitative comparison of seven epsilon-ring occultation profiles obtained over a period of 3.4 yr reveals a consistent structure, which may reflect the presence of unresolved gaps and subrings.

Nicholson, P. D.↗
NASA NTRS1982

Effect of orthotropic properties and panel width on the compression strength of graphite-epoxy laminates with holes

An experimental study conducted to evaluate the effect of laminate orthotropic properties and panel width on the compression strength of 48-ply graphite-epoxy laminates with drilled holes is described. The test results are evaluated on the basis of hole size and specimen width and are used in determining parameters necessary for predicting trends using the point stress failure criterion. Good agreement is obtained between experimental and predicted values of failure for panels fabricated from two quasi-isotropic laminates and one orthotropic laminate. The results suggest that panels of different widths having holes that are large in relation to the failure prediction parameter should be included in any test program conducted to develop prediction trends that may be used in design applications.

Rhodes, M. D.↗
NASA NTRS1983

Finite-width currents, magnetic shear, and the current-driven ion-cyclotron instability

Our earlier results that non-local effects due to even a small magnetic shear produce a significant reduction of the growth rate of the ion cyclotron instability driven by a uniform current are now generalized to finite width currents. Externally prescribed as well as self-consistent shears are considered. If the current width Lc exceeds the shear length Ls, the previous results are recovered. Shear becomes less effective with reduction of Lc, and for typical parameters, the growth rate attains its (shearless) local value for Lc/Ls approximately less than 10 to the minus 2. Non-local effects of the finite current width itself come into play if Lc is further reduced to a few ion Larmor radii and can quench the instability. Previously announced in STAR as N83-28996

Bakshi, P.↗
NASA NTRS1985

Pulse-Width-to-Analog-Voltage Converter

Peak output voltage varies linearly with input-pulse duration. Circuit converts pulses of varying widths (as from sound-velocity instrumentation or tachometers) into analog voltages. Peak voltage increases in proportion to pulse width. Voltage used to drive an x-y plotter or storage oscilloscope. Pulse-width-to-voltage converter has peak output voltage that varies with duration of input pulses.

Sosack, G. S.↗
NASA NTRS1985

Extremely metal-deficient red giants. IV - Equivalent widths for 36 halo giants

Further work on a study of 36 metal-poor field red giants is reported. Chemical abundances previously determined were based on model stellar atmosphere analyses of equivalent widths from photographic image-tube echelle spectrograms obtained with with 4-m reflectors at Kitt Peak and Cerro Tololo. A tabulation of the equivalent-width data (a total of 18, 275 equivalent widths) is presented.

Luck, R. E.↗