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Parkinson, W. H.

Publications and source records attributed to Parkinson, W. H..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Transition probability of the Si III 189.2-nm intersystem line

Measurement of the lifetime of the metastable 3s3p(3)P(0)1 level of Si(2+) (Si III), which decays by photon emission at 189.2 nm to the 3s2(1)S0 state, is reported. The data were taken from spontaneous emission from metastable Si III stored in an RF ion trap. The Si III ions were produced through electron bombardment of SiH4 and SiF4 at pressures of 1/100,000,000-1/10,000,000 Torr. A photomultiplier was employed to count the photon emissions from the transitions. A total of 11 decay curves were generated for analysis, with Poisson statistics used to set the uncertainties at within 8 pct. Significant systematic effects were controlled, and the lifetime was found to be within 3.6 microsec of 59.9 microsec. The method used is concluded valid for determining the lifetimes of metastable levels of low-Z ions with low charge, and thereby the transition probabilities.

Kwong, H. S.↗
NASA NTRS1982

Laser-excitation technique for the measurement of absolute transition probabilities of weak atomic lines

A new technique is presented for the measurement of transition probabilities for weak allowed, intersystem, and forbidden lines. The method exploits the fact that oscillator strength is proportional to the number of stimulated absorptions and emissions produced by a narrow-band laser pulse of known energy which is in resonance with an atomic transition. The method is tested for a particular transition of Mg I with a known oscillator strength value and of appropriate magnitude. The number densities are measured using a Mach-Zehnder interferometer and the hook method for the lower level population and by measuring an absorption-equivalent width for the other. The apparatus consisted of a high-power tunable laser and a magnesium oven to produce excited Mg vapor, and a laser-plasma background continuum. The results are in good agreement with theoretical and other experimental data.

Kwong, H. S.↗
NASA NTRS1981

Vacuum ultraviolet Mach-Zehnder interferometer with CaF2 optics

CaF2 beam splitters and compensation and test cell windows have been installed in a VUV Mach-Zehnder interferometer. Results of an evaluation of their performance in the VUV, namely, a measurement of the oscillator strength (f value) of the resonance transition at atomic xenon at 146.9610 nm are reported.

Smith, P. L.↗
NASA NTRS1980

Solar spectral radiance and irradiance at 225.2-319.6 nanometers

Mean absolute intensities (spectral radiance) over 0.1 nm intervals between 225.2 nm and 319.6 nm at disk center and near the limb of the sun (mu = 0.23 + or - 0.04) are derived from the high spectral resolution measurements published by Kohl, Parkinson, and Kurucz. The corresponding limb-to-center ratios and spectral irradiance values are provided. A comparison with existing measurements of solar spectral radiance and spectral irradiance for the most part shows agreement within the estimated error limits, although some narrow band variations may be outside experimental errors. The contribution to the solar constant of the 230-305 nm band is derived to be 19.7 W/square m + or - 12%.

Kohl, J. L.↗
NASA NTRS1980

Measurements of coronal kinetic temperatures from 1.5 to 3 solar radii

A rocket-borne Lyman-alpha coronagraph has been used to make the first measurements of the spectral line profile of resonantly scattered hydrogen Lyman-alpha coronal radiation between 1.5 and 3 solar radii. These data provide, for the first time, direct measurements of coronal temperatures above 1.5 solar radii. Data were obtained in a coronal hole, quiet region, and streamer. The widths of the profiles from the quiet region decrease with height and correspond to a steady decrease in hydrogen kinetic temperature, with increasing radius, from about 2.5 million K at r = 2 solar radii to about 1 million K at r = 9 solar radii. In the coronal hole the measured line widths indicate a kinetic temperature of 1.8 million K at r = 2.5 solar radii.

Kohl, J. L.↗
NASA NTRS1980

Photoelectric scanning /6.65-m/ spectrometer for VUV cross-section measurements

A 6.65-m normal incidence vacuum spectrograph has been provided with a photoelectric scanner that is easily interchangeable with the original plate holder. The scanner consists essentially of a photoelectric detector and an exit slit that scans mechanically along the focal surface while the grating and entrance slit remain stationary. The design and construction of the 6.65-m scanning spectrometer, which operates in the 120-300-nm wavelength region, are discussed. The wavelength resolution of 0.001 nm obtained photoelectrically is better than that of any existing vacuum monochromator. The performance of the instrument is illustrated with vacuum ultraviolet scans of the (1, 5) band of fourth positive system of CO in emission, and the (14, 0) band of the Schumann-Runge system of O2 in absorption.

Yoshino, K.↗
NASA NTRS1979

High current hollow cathode tube as a source of metastable atoms

A source for the continuous production of neutral metastable atoms is described. A hollow cathode discharge tube was used to produce densities of 3.5 times 10 to the 13th per cu cm and column densities of 1.6 times 10 to the 15th per sq cm in the 4s(2)2D metastable term of neutral copper. The accuracy of these density determinations (+ or - 30 to + or - 66%) is limited by the oscillator strengths required for the analysis. The usefulness of the source was demonstrated by measurements of relative oscillator strengths of some Cu I lines in the 2200 A wavelength region. These data are compared with those obtained by other methods.

Lombardi, G. G.↗
NASA NTRS1979

Computer assisted performance tests of the Lyman Alpha Coronagraph

Preflight calibration and performance tests of the Lyman Alpha Coronagraph rocket instrument in the laboratory, with the experiment in its flight configuration and illumination levels near those expected during flight were successfully carried out using a pulse code modulation telemetry system simulator interfaced in real time to a PDP 11/10 computer system. Post acquisition data reduction programs developed and implemented on the same computer system aided in the interpretation of test and calibration data.

Parkinson, W. H.↗
NASA NTRS1979

High resolution atmospheric transmission calculations down to 28.7 km in the 200-243-nm spectral range

Decrease in stratospheric ozone absorption and increase in oxygen absorption with decreasing wavelength combine to produce a window of maximum atmospheric transmission near 210 nm. Since solar radiation in this spectral region dissociates molecular oxygen, the deep atmospheric penetration at this wavelength is of particular aeronomical interest. High resolution calculations of the transmittance down to 28.65 km were made for the 200-243-nm spectral range in this window region, in support of a stratospheric balloon flight from Fort Churchill in July 1974. The calculations were made by dividing the atmosphere into layers which were chosen so that each could be assumed homogeneous; optical depths were calculated separately for each of these layers and then summed to obtain the over-all transmittance of the atmosphere. Absorption by molecular oxygen (line and continuum) and by ozone was included, as well as extinction through Rayleigh scattering by air molecules. The calculated transmittances were combined with high altitude (above 100-km) rocket measurements of the sun-center spectrum and center-to-limb variations to give residual high resolution solar spectral flux for several altitudes and solar zenith angles.

Cann, M. W. P.↗
NASA NTRS1978

Absolute cross section for photoionization of atomic oxygen

The absolute cross section for photoionization of atomic oxygen from the 2p4 3P ground state of O(0) to the 2p3 4S ground state of O(+) has been measured at five narrow wavelength intervals between 89.8 and 76.2 nm. The cross section near the 2p3 4S threshold is 4.5 Mb + or - 7%. Recent calculations by Taylor and Burke (1976) and by Pradhan and Saraph (1977) are in reasonable agreement with this work. The dipole-length results of Taylor and Burke (4.1 Mb) are in better agreement with the experiment than their dipole-velocity results (3.2 Mb).

Kohl, J. L.↗
NASA NTRS1978

Center and limb solar spectrum in high spectral resolution 225.2 nm to 319.6 nm

The atlas has been designed to fulfill the need in solar and stellar astronomy, in aeronomy, and in space science for a convenient reference source that provides a detailed and accurate record of the measured solar ultraviolet spectrum in high spectral resolution for the wavelength range from 225.2 nm to 319.6 nm. The atlas also contains a preliminary synthetic solar spectrum with a legend for identifying and describing the features of the synthetic spectrum. Attention is given to aspects of instrumentation, the radiometric calibration, the wavelength scale, background noise random fluctuations and data filtering, intermittent noise, the observational conditions, the experimental uncertainty, the atlas format, references, tables, and plots.

Kohl, J. L.↗
NASA NTRS1977

The solar boron abundance

Positive evidence for the presence of boron in the sun is reported, and the chemical abundance of boron in the photosphere is derived from photoelectric measurements of the solar spectrum near 2500 A obtained with a rocketborne high-resolution spectrometer. Short sections of the spectrum in the vicinities of the B I lines at 2496.772 and 2497.723 A are plotted. The photospheric boron abundance is determined primarily by analyzing the solar-center spectrum near the first of the two lines in the framework of several single-component photospheric models. The logarithmic boron abundance obtained is 2.6, with an estimated uncertainty of plus or minus 0.3 dex, on the scale where that of hydrogen is 12.0. This value is shown to be in excellent agreement with that predicted for a nucleosynthesis model in which Li, Be, and B are produced by cosmic-ray spallation.

Kohl, J. L.↗
NASA NTRS1976

Measurements of Sc I gf-values

Absolute gf-values were obtained for 98 transitions in neutral scandium by the hook method using an inductively coupled heat-pipe oven. Of the 98 lines, 51 are classified, 33 are unclassified lines that occur in pairs with the lower energy level identified, and 14 are unclassified but are believed to originate from one of the two lower levels of the ground state. The results are compared with semiempirical and other measurement results in the literature.

Parkinson, W. H.↗