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NASA NTRS1974

Prediction and identification of some forbidden lines in the Ne I sequence

A magnetic quadrupole transition which according to a prediction by Garstang (1969) is to have an appreciable transition probability in the higher ions of the Ne I sequence has recently been observed in Fe XVII with high resolution by Parkinson (1973), at 17.086 A. Values of an interval predicted by calculations of Crance (1973) are plotted in a graph. Interval values obtained from the curve are used to predict the values of certain transition wavelengths in the ions Si V Cr XV.

Kastner, S. O.↗

NASA NTRS1975

Na-22, Ne-E, extinct radioactive anomalies and unsupported Ar-40

The possibility that the origin of extinct radioactivities depended on their living long enough for grains to form in the expanding nucleosynthetic envelope, rather than on their living long enough for meteorites to form, is examined. As an example, the interpretation of Na-22 as a detectable extinct radioactivity, with a half life of only 2.6 years, is explored and related to Ne-22 occurrence. Similar arguments involving He-4, Ar-40, K-40, K-41, and calcium, titanium, chromium, manganese, iron, nickel, and cobalt isotopes are briefly presented.

Clayton, D. D.↗

NASA NTRS1975

Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center

High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.

Wollman, E. R.↗

NASA NTRS1976

Spectral and spatial resolution of the 12.8 micron Ne II emission from the galactic center

High-resolution spectra of the Ne II 12.8-micron fine-structure line in emission from the galactic-center cloud Sgr A West show a line-center LSR radial velocity of +75 (+ or - 20) km/s and a velocity dispersion of about 200 km/s. The line has been observed with spectral resolution as high as 0.10 micron/cm and spatial resolution as high as 8 arcsec. This appears to provide a direct measurement of conditions in the 45-arcsec ionized region at the galactic center. The radial velocity and dispersion are more or less independent of position and indicate that events as recent as the last 10,000 years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit of the order of 4 million solar masses for the mass within 0.8 pc of the galactic center is obtained from the velocity dispersion.

Wollman, E. R.↗

NASA NTRS1976

Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

Walton, J. R.↗

NASA NTRS1977

Ne II 12.8 micron emission from the galactic center. II

Recent observations of the 12.8-micron Ne II emission from the galactic center have revealed a region of primarily blueshifted emission in addition to the previously detected redshifted emission. It appears most likely that the blueshifted and redshifted emission come from separate clouds and that the dynamics of the ionized gas is dominated by the gravitational potential of the massive core at the galactic center. On the basis of the velocities and velocity dispersions, the total mass within a radius of 1 pc about the galactic center is estimated to be of the order of 4 million solar masses.

Wollman, E. R.↗

NASA NTRS1978

Infrared observations of the galactic center. II - Forbidden Ne II emission

The forbidden Ne II line flux has been measured with a 5-arcsec diaphragm at eight positions in the galactic-center (Sgr A-West) region. The line fluxes - and hence the density of ionized gas - are not correlated with the presence of discrete compact sources of 10-micron continuum radiation. The discrete sources probably contain sources of energy that heat nearby dust instead of being regions of enhanced dust density.

Willner, S. P.↗

NASA NTRS1978

Ne II 12.8 micron emission and galactic dynamics in M82

Ne II fine-structure emission at 12.8 microns from the galaxy M82 has been spatially and spectrally resolved. This radiation is relatively unaffected by obscuration, scattering, or maser amplification, and should hence provide a more reliable map of the velocity field within the galaxy than do optical or radio observations. A recessional velocity of 215 + or - 20 km/s is found for the galaxy, and a much steeper rotation curve is obtained than that from optical measurements. Furthermore, there is evidence for large-scale noncircular motion of the gas within the inner 150 pc of the nebula. The results are consistent with the idea that the peculiarities of M82 are due to collision with an intergalactic dust cloud as suggested by Solinger, Morrison, and Markert (1977).

Beck, S. C.↗

NASA NTRS1978

Measurements of pulse-height defect in Au-Si detectors for H, He, C, N, O, Ne, Ar, Kr from about 2 to 400 keV/nucleon

We report measurements of pulse-height defects in Si surface-barrier detectors for a variety of ions and energies. We find: (1) for ions up to Ne our measurements agree remarkably well with calculations based on energy loss and nuclear defect theory, (2) for heavier ions we find systematic deviations, (3) there is no evidence of a dead layer at the Si-Au interface, and (4) our measurements are consistently reproducible for detectors fabricated in our laboratory.

Ipavich, F. M.↗

NASA NTRS1980

The mean-mass of cosmic-ray Ne, Mg and Si at 1.0 GeV/amu

The results of a new measurement of the mean mass of the cosmic-ray nuclei Ne, Mg and Si at an energy of 1.0 GeV/amu are presented. The method employs the filtering effect of the geomagnetic field on the incoming cosmic-ray fluxes. The results were obtained in two balloon flights from Muskogee, Oklahoma (vertical cutoff rigidity = 3.4 GV) yielding an exposure factor of 20 sq m srh. The instrument consists of a counter telescope containing 2 plastic scintillators, 2 Cerenkov radiators and a multiwire proportional chamber hodoscope for trajectory identification.

Dwyer, R.↗

NASA NTRS1983

Abrasion cross sections for Ne-20 projectiles at 2.1 GeV/nucleon

Utilizing eikonal scattering theory, an optical model potential approximation to the exact nucleus-nucleus multiple scattering series is used in an abrasion-ablation collision formalism to predict abrasion cross sections for relativistic Ne-20 projectile nuclei. Excellent agreement with recent experimental abrasion results is obtained. The sensitivity of the abrasion predictions to Pauli exclusion principle correlation effects and to the assumed shape of the nuclear single-particle density distribution is also demonstrated.

Townsend, L. W.↗

NASA NTRS1984

The (20)Ne interaction in extended matter

Although heavy ion transport theory is developed to a relatively advanced stage, the present limitation in biomedical and electronic applications is the uncertainty in nuclear fragmentation parameters. The present status on Ne-20 beams is discussed and useful formulae are presented for future use in analysis of beam transport experiments.

Wilson, J. W.↗

NASA NTRS1985

Total electron scattering cross sections. I - He, Ne, Ar, Xe

The apparatus and experimental procedures used to obtain total electron scattering cross sections are described, and results are presented for He, Ne, Ar and Xe in the 4-300 eV incident energy range, together with statistical errors. The results are generally found to be in good agreement with previous data except at low impact energies. Serious discrepancies remain in Xe below 20 eV impact energy.

Nickel, J. C.↗

NASA NTRS1983

Fragmentation of approximately 500 MeV/nuc Ne and O nuclei in CH2, C and H targets - Charge and isotopic cross sections

Fragmentation of Ne-20 and O-16 nuclei in CH2 and C targets at several energies between 400 and 1000 MeV/nuc is carried out in order to obtain cross sections in hydrogen for use in the galactic cosmic ray propagation problem. Charge changing and isotopic cross sections for the fragments with Z greater than or equal to 4 are obtained. The hydrogen cross sections are obtained by a subtraction procedure. The predictions of the semi-empirical model of Tsao and Silberberg (1979) are given and in general there is good agreement between the measurements and the predictions.

Webber, W. R.↗

NASA NTRS1986

Redetermination of parameters for semi-empirical model for spallogenic He and Ne in chondrites

A semi-empirical model described previously satisfactorily reproduced a number of shielding-dependent variations in the relative production rates of spallogenic He and Ne in chondrites. However, data for cores of the Keyes and St. Severin meteorites showed a subsurface build-up in He-3 which was not predicted with the original model parameters and the model was not pursued. Renewed interest in the preatmospheric size of meteorites, spurred in part by the desirability of understanding the exposure history of the SNC meteorites, justifies redetermination of model parameters.

Nyquist, L. E.↗

NASA NTRS1985

Density sensitive X-ray line ratios in the Be I, B I, and Ne I isoelectronic sequences

The intensities of X-ray transitions in highly charged ions in the Be I, B I, and Ne I isoelectronic sequences have been calculated as functions of electron density. The intensities of the transitions from the 2s(n)2p(m)3p configuration, relative to the intensities from the 2s(n)2p(m)3s and 2s(n)p(m)3d configurations, are strong functions of electron density in high-density plasmas. The density sensitivity occurs at electron densities between 10 to the 16th/cu cm (for Si ions) and 10 to the 22nd/cu cm (for Kr ions). Opacity is unimportant for plasma dimensions that are characteristic of dense laser-produced plasmas. These X-ray line ratios represent a promising new density diagnostic for high-density plasmas.

Feldman, U.↗

NASA NTRS1986

He-Ne and CW CO2 laser long-path systems for gas detection

This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual CW carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.

Grant, W. B.↗

NASA NTRS1986

A full CI treatment of Ne atom - A benchmark calculation performed on the NAS CRAY 2

Full CI calculations are performed for Ne atom using Gaussian basis sets of up to triple-zeta plus double polarization quality. The total valence correlation energy through double, triple, quadruple and octuple excitations is compared for eight different basis sets. These results are expected to be an important benchmark for calibrating methods for estimating the importance of higher excitations.

Bauschlicher, C. W., Jr.↗