Engineering topics
Publications and source records attributed to Smith, W. H..
Upper limits are placed on the D/H ratio in the observed portions of the atmospheres of Jupiter and Saturn from observations at high S/N over the region of the 5-0 R(1) line of HD. The upper limits of 0.00004 and 0.00006 D/H on Jupiter and Saturn, respectively, are not inconsistent with present models for abundance ratios in the primitive solar nebula or with other estimates of this quantity from observations.
A model for the Venus atmosphere involving photochemistry of oxygen, hydrogen, chlorine and sulfur species is presented. Sulfur reaction schemes and hydrogen and chlorine reaction schemes were included. The impact of sulfur on the oxygen budget and the subsequent production of H2SO4 molecules for the Venus cloud deck were explored. A major new reaction scheme for production of H2SO4 molecules involving sulfur and oxygen chemistry was established shown to dominate over the odd hydrogen scheme proposed earlier. The efficiency of the scheme in formation of H2SO4 is only about 50%, with the remaining sulfur residing in SO2 molecules. The calculated downward flux of H2SO4 may be sufficient to maintain a steady state sulfuric acid cloud if the resident time of H2SO4 droplets in the cloud is as long as a few years. If however, the resident time is half a year or shorter, additional chemistry capable of more efficient conversion of SO2 to SO3 is required.
The HD 5-0 R(0) line on Saturn and Uranus has been observed. Values for the D/H abundance ratio computed from models for the atmospheres of these two planets are 5.5 + or - 2.9 times 10 to the minus fifth power for Saturn and 3.0 + or - 1.2 times 10 to the minus fifth power for Uranus. The D/H ratio for Jupiter of 5.1 + or - 0.7 times 10 to the minus fifth power found from a measurement of the HD 4-0 P(1) line is bracketed by the values found for Saturn and Uranus.
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The ratio for the equivalent widths for the unsaturated H2 quadrupole transitions observed in the Jovian planets is calculated and compared with a large number of observations. The comparison indicates that equilibrium hydrogen may be present in Jupiter and Saturn, while Uranus and Neptune exhibit ratios not in accord with equilibrium hydrogen. Observations which can differentiate among the possible states of H2 are proposed.
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Most work in recent years on the unidentified diffuse interstellar bands has been concentrated on the hypothesis that they are produced by some process in solid grains. We review that hypothesis and the arguments which support it, and find that diffuse band formation by certain classes of molecules should not yet be ruled out. Since several relevant observations have been made in the last four years, the observational data on the bands are reviewed. It would appear that these data are as consistent with molecular origins for the bands as with grain origins. Types of molecular transitions which give rise to 'diffuse' bands are described. These transitions can occur in relatively simple molecules composed of cosmically abundant elements and can produce broad, unresolvable profiles without destroying the molecule. New observations are suggested which could produce decisive evidence with which to determine whether the diffuse bands originate in grains, molecules, or both.
The paper reports on a search for the (8, 0) R(0) line of the A-X transition of NaH at 3990.88 A toward Zeta Oph and Sigma Sco, which was performed using a spectroscopic photoelectric imaging Fabry-Perot interferometer at the coude focus of a 2.2-m telescope. One-sigma upper limits on the NaH equivalent width are derived (0.26 mA for Zeta Oph and 0.69 mA for Sigma Sco), and two-sigma upper limits on the NaH column densities are obtained which imply that the formation rate for NaH cannot be large. It is noted that the latter upper limits are only about one order of magnitude higher than the most optimistic expectation of the NaH column density for formation of this molecule on grains.
We present the results of an analysis of the effects of atmospheric seeing and of instrumental spectral and spatial resolution on the observed variation of absorption-line profiles across the disk of Jupiter. The technique described may be applied equally well to the analysis of observations of any extended astronomical source. These results show the necessity of obtaining accurate point-spread-function information during the course of observations of this nature. We also point out that in order to avoid the uncertainties and ambiguities inherent in attempts at deconvolution of observational data, one must properly convolve the appropriate spatial and spectral resolution functions with the models being tested and then compare the results with the observational data.
A Fabry-Perot interferometer was used to measure a 2-sigma upper limit of 0.39 mA for CH(plus) toward Tau Sco, a line of sight with a large amount of atomic hydrogen yet only a small amount of molecular hydrogen. The upper limit for the abundance of CH(plus) in a region where hydrogen is primarily atomic shows that no unexpectedly rapid CH(plus) formation processes are occurring and, conversely, that the CH(plus) destruction rate is not smaller than expected. It is argued that either CH(plus) is primarily formed in regions with large amounts of H2 or CH(plus) is formed at least as rapidly as the density-cubes in regions where hydrogen is mostly atomic.
A high-resolution spectrum of the series of lines near 6825 A presumably due to CH4 has been obtained for Uranus. The line spacings are in agreement with the previous observations of Owen (1966), Bergstralh (1975), and Belton and Hayes (1975) but not with the laboratory observations reported by Lutz and Owen (1976). It is proposed that the transitions identified by Lutz and Owen are not correlated one-to-one with those features observed in the planets. Wavelength differences of up to 0.8 A are found between the laboratory and planetary features, where the resolving power allows one to specify the line positions to better than + or - 0.07 A. The spectrum obtained for Neptune is in essential agreement with that for Uranus.
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In order to observe extended astronomical objects at high spatial and spectral resolution, we have constructed a spectroscopic photoelectric imaging Fabry-Perot interferometer (SPIFI). Among the properties chosen for the instrument are an air-spaced, piezoelectrically scanned design allowing an accurately settable free spectral range and employing a single etalon of high finesse. Careful design of the etalon mountings and optical train preserves high light throughput. We either obtain spectra of single spatial elements with a photomultiplier or use an SEC vidicon detector to record a series of images through the interferometer while scanning the wavelength in discrete steps. The latter procedure yields sufficient information to reconstruct spectral features over the entire object. For the conditions assumed, either series of observations requires only a small fraction of a rotational period for Jupiter or Saturn, for example.
The upper states of the OH and OD bands in the region between 1700 and 1950 A have been studied with a phase-shift radiative lifetime apparatus. Lifetimes varying from 1.8 to 2.9 ns have been found. Lifetimes for OH and OD are essentially the same, indicating that the upper states are likely to be depopulated via purely radiative processes under the present experimental conditions. Lifetimes have also been obtained for the C(2)Sigma(+) - A(2)Sigma(+) transition in OH and OD. These results are consistent with the preliminary analysis of Pryce (private communication) that the bands between 1700 and 1950 A in OH are partly due to the C(2)Sigma(+) - X(2)Pi sub i transition.
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In order to observe extended astronomical objects at high spatial and spectral resolution, a spectroscopic photoelectric imaging Fabry-Perot interferometer was constructed. Among the properties chosen for the instrument are an air-spaced, piezoelectrically scanned design allowing an accurately settable free spectral range and employing a single etalon of high finesse. Careful design of the etalon mountings and optical train preserves high ligh throughput. Spectra of single spatial elements with a photomultiplier were obtained, and an SEC vidicon detector was used to record a series of images through the interferometer while scanning the wavelength in discrete steps. The latter procedure yields sufficient information to reconstruct spectral features over the entire object, and for the conditions assumed, either series of observations requires only a small fraction of a rotational period for Jupiter or Saturn. An electronic control system was also constructed which permits rapid and flexible variation of the operational mode of the Fabry-Perot and its ancilliary devices so as to minimize loss of observational time.
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