Comet kohoutek: ultraviolet images and spectrograms

Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 x 10(29) atoms per second.     

Extreme ultraviolet observations from voyager 1 encounter with saturn

The global hydrogen Lyman alpha, helium (584 angstroms), and molecular hydrogen band emissions from Saturn are qualitatively similar to those of Jupiter, but the Saturn observations emphasize that the H(2) band excitation mechanism is closely related to the solar flux. Auroras occur near 80 degrees latitude, suggesting Earth-like magnetotail activity, quite different from the dominant Io plasma torus mechanism at Jupiter. No ion emissions have been detected from the magnetosphere of Saturn, but the rings have a hydrogen atmosphere; atomic hydrogen is also present in a torus between 8 and 25 Saturn radii. Nitrogen emission excited by particles has been detected in the Titan dayglow and bright limb scans. Enhancement of the nitrogen emission is observed in the region of interaction between Titan's atmosphere and the corotating plasma in Saturn's plasmasphere. No particle-excited emission has been detected from the dark atmosphere of Titan. The absorption profile of the atmosphere determined by the solar occultation experiment, combined with constraints from the dayglow observations and temperature information, indicate that N(2) is the dominant species. A double layer structure has been detected above Titan's limb. One of the layers may be related to visible layers in the images of Titan.     

Rocket ultraviolet spectrophotometry of comet kohoutek (1973f)

Observations of Comet Kohoutek (1973f) in the spectral region between 1200 and 3200 angstroms were made from an Aerobee rocket on 5.1 January 1974 universal time. The strongest features observed were the Lyman alpha line of neutral atomic hydrogen at 1216 angstroms and the hydroxyl (OH) bands at 3090 and 3142 angstroms. Atomic oxygen and atomic carbon were also detected, and their luminosity implies a production rate (of carbon monoxide or carbon dioxide) commensurate with that of water vapor.     

X-ray line and continuum spectra of solar flares from 0.5 to 8.5 angstroms

Two crystal spectrometers aboard the orbiting solar observatory OSO-4 cover the wavelength ranges 0.5 to 3.9 angstroms and 1.0 to 8.5 angstroms. Within this range, there appear emission lines from hydrogen-like and helium-like states of calcium, sulfur, silicon, magnesium, and aluminum. The Mg XII Lyman-alpha is present strongly in all x-ray flares. The most intense flares (such as class 3) produce strong Si XIV Lyman-alpha and often S XVI Lyman-alpha. Emission, in the form of Ka lines of highly ionized states of calcium, iron, aluminum, and silicon is usually present. The continuum from 1 to 10 angstroms always dominates the line emission by more than an order of magnitude. Electron temperatures derived from the slope of the continuum spectrum are in the range of 10(7) to 10(8) degrees K, considerably higher than theoretical ionization equilibrium temperatures.     

Space plasma physics: atmospheric emissions photometric imaging experiment

The atmospheric emissions photometric imaging experiment was flown on Spacelab 1 to study faint natural and artificial atmospheric emission phenomena. The instrument imaged optical emission in the region 2000 to 7500 angstroms with a television system consisting of two optical channels, one wide-angle and one telephoto. A third optical channel imaged onto the photochathode of a microchannel plate photomultiplier tube that has 100 discrete anodes. A hand-held image intensifier camera with an objective grating permitted spectral analysis of the earth's airglow and the shuttle glow. Preliminary data show magnesium ion emission features in the lower ionosphere as well as the spececraft glow spectrum.     

Apollo 16 far-ultraviolet camera/spectrograph: Earth observations

A far-ultraviolet camera/spectograph experiment was operated on the lunar surface during the Apollo 16 mission. Among the data obtained were images and spectra of the terrestrial atmosphere and geocorona in the wavelength range below 1600 angstroms. These gave the spatial distributions and relative intensities of emissions due to atomic hydrogen, atomic oxygen, molecular nitrogen, and other species-some observed spectrographically for the first time.     

Detection of singly ionized oxygen around jupiter

Forbidden emission from singly ionized oxygen at wavelengths of 3726 and 3729 angstroms has been detected in the inner Jovian magnetosphere. The emission is present between approximately 4 and approximately 7 to 8 Jovian radii from the planet and appears concentrated in the magnetic equator. The line intensity ratio indicates the same plasma characteristics as those derived from observations of forbidden sulfur emission.     

Molecular diffuse interstellar band carriers in the red rectangle

High-resolution optical spectroscopic observations of unidentified emission bands from the unusual biconical nebula known as the Red Rectangle are reported. The peak wavelengths and the widths of prominent bands near 5799, 5853, and 6616 angstroms decrease with increasing offset from the central A0-type star HD 44179 and, in the limit of large distance from the star, are shown to converge toward the known values for some of the narrower diffuse interstellar absorption bands at 5797, 5850, and 6614 angstroms. The same carriers give rise to both Red Rectangle emission and corresponding diffuse interstellar absorption bands, and these particular bands arise from electronic transitions in gas-phase molecules.     

A monoclinic post-stishovite polymorph of silica in the shergotty meteorite

A post-stishovite phase of silica was identified in the Shergotty meteorite by x-ray diffraction and field emission scanning electron microscopy. The diffraction pattern revealed a monoclinic lattice, similar to the baddeleyite-structured polymorph with the cell parameters a = 4.375(1) angstroms, b = 4.584(1) angstroms, c = 4. 708(1) angstroms, beta= 99.97(3), rho = 4.30(2) grams per cubic centimeter, where the numbers in parentheses are the maximum deviations. Transmission electron microscopy investigations indicate the presence of the alpha-lead dioxide-like polymorph, stishovite, and secondary cristobalite in the same silica grain. The mixture of high-density polymorphs suggests that several post-stishovite phases were formed during the shock event on the Shergotty parent body.     

Soft X-ray Images of the Solar Corona with a Normal-Incidence Cassegrain Multilayer Telescope

High-resolution images of the sun in the soft x-ray to extreme ultraviolet(EUV) regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 angstroms. The bandpass centered at 173 angstroms is dominated by emission from the ions Fe IX Fe X. This emission is from coronal plasma in the temperature range 0.8 x 10(6) to 1.4 x 10(6)K. The images have angular resolution of about 1.0 to 1.5 arc seconds, and show no degradation because of x-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to overlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.     

Neutron diffraction of cell membranes (myelin)

Small-angle neutron diffraction (wavelength 4.05 angstroms) of human and rabbit sciatic nerve has been carried out by means of the Brookhaven high flux beam reactor with an automated slit camera. Most of the free water of the nerves was substituted in order to minimize incoherent scatter of hydrogen atoms. The differences in amplitude and phase shifts between neutrons and x-rays resulted in a neutron diffraction pattern that was completely different from the x-ray pattern. The neutron pattern consisted of a single peak of about 89-angstrom spacing in the region examined (up to 6-angstrom spacing). The strong third, fourth, and fifth order reflections (about 60, 45, and 36 angstroms) seen in the x-ray pattern were suppressed. The neutron data indicated a strong scattering from one portion of the membrane.     

Ultraviolet spectroscopy of venus: initial results from the pioneer venus orbiter

Ultraviolet spectroscopy of the Venus cloud tops reveals absorption features attributed to sulfur dioxide in the atmosphere above the cloud tops. Measurements of scattered sunlight at 2663 angstroms show evidence for horizontal and vertical inhomogeneities in cloud structure. Images of the planet at SO(2) absorption wavelengths show albedo features similar to those seen at 3650 angstroms from Mariner 10. Airglowv emissions are consistent with an exospheric temperatuire of approximately 275 K, and a night airglows emission has been detected, indicating the precipitation of energy into the dark thermosphere.     

Magnetospheric dayside cusp: a topside view of its 6300-angstrom atomic oxygen emission

An interference filter photometer on the ISIS-1l spacecraft generates global maps of the atomic oxygen emission at 6300 angstroms from the ionosphere. The most prominent feature observed is a band of permanent red aurora on the dayside of the earth, centered on magnetic noon at about 78 degrees magnetic (invariant) latitude, brighter than the quiet-time nightside aurora.     

Photon emission at molecular resolution induced by a scanning tunneling microscope

The tip-surface region of a scanning tunneling microscope (STM) emits light when the energy of the tunneling electrons is sufficient to excite luminescent processes. These processes provide access to dynamic aspects of the local electronic structure that are not directly amenable to conventional STM experiments. From monolayer films of carbon-60 fullerenes on gold(110) surfaces, intense emission is observed when the STM tip is placed above an individual molecule. The diameter of this emission spot associated with carbon-60 is approximately 4 angstroms. These results demonstrate the highest spatial resolution of light emission to date with a scanning probe technique.     

Photolytic cleavage of sulfonamide bonds

It has been found that the sulfonamide bond is relatively susceptible to photolytic cleavage. The breakdown was effected either by irradiation with a source having a continuous emission above the wavelengths of 1800 angstroms or by another source emitting principally at 2537 angstroms. Less destruction of the amino acids was seen with the latter relative to the sulfonamide bond cleavage. The cleavage was not effected by irradiation at wavelengths greater than about 3000 angstroms. Side reactions were noted involving decarboxylation, demination, and destruction of certain susceptible amino acids such as tryptophan. In only one case was a product found that arose from cleavage of a carboxamide bond; glycyltyrosine gave glycine and tyrosine upon irradiation. A yield of 75 percent of the corresponding amino acid has been obtained by irradiation of tosylhistidine; yields of 75 to 100 percent have been obtained from sulfamic acid (NH(2)SO(3)H). A qualitative method for identifying sulfonylated amino acids is described.     

Monoclinic hydroxyapatite

The existence of a monoclinic phase of hydroxyapatite, Ca(2)(PO(4))(4)OH, has been confirmed, by single-crystal structure analysis (weighted "reliability" factor = 3.9 percent on |F|(2)). The structure has space group P21/b, a = 9.4214(8) angstroms, b = 2a, c = 6.8814(7) angstroms, and gamma = 120 degrees , and is analogous to that of chlorapatite. The distortions from the hexagonal structure with which the monoclinic structure is pseudosymmetric are similar to those in chlorapatite, including enlargement of that triangular array of oxygen atoms in which the chlorine ion or, in hydroxyapatite, the hydroxyl hydrogen ion is approximately centered. The hydroxyapatite specimen was prepared by the conversion of a single crystal of chlorapatite in steam at 1200 degrees C, was mimetically twinned, and was approximately 37 percent monoclinic.     

Crystalline transfer RNA: the three-dimensional Patterson function at 12-angstrom resolution

An orthorhombic form of crystalline formylmethionine transter RNA has been obtained which contains one molecule as the asymmetric unit of the unit cell. Three-dimensional x-ray diffraction data have been collected up to a resolution of 12 angstroms, and from this a Patterson function has been calculated. The function contains an elongated ridge of interatomic vectors parallel to the c-axis of the crystal. Analysis of the function suggests that the molecules are elogated and dimerized in an overlapping antiparrael fashion along the c-axis. The dimer has a length near 109 angstroms and a width of 35 angstroms in one direction. The individual molecular length is approximately 80 angstroms with an irregular cross section measuring 25 by 35 angstrms.     

Mercury's Atmosphere from Mariner 10: Preliminary Results

Analysis of data obtained by the ultraviolet experiment on Mariner 10 indicates that Mercury is surrounded by a thin atmosphere consisting in part of helium. The partial pressure of helium at the terminator is about 5 x 10(-12) millibar. The total surface pressure of the atmosphere is less than about 2 x 10(-9) millibar. Upper limits are set for the abundance of various gases, including hydrogen, oxygen, carbon, argon, neon, and xenon. The wavelength dependence of Mercury's surface albedo is similar to that of the moon over a broad range of wavelengths from 500 to 1600 angstroms. Strong signals were recorded by the airglow instrument as Mariner 10 passed through the cavity behind Mercury. They are as yet unexplained but may provide information on the properties of the local plasma.     

Protein, DNA, and virus crystallography with a focused imaging proportional counter

A set of programs has been developed for rapid collection of x-ray intensity data from protein and virus crystals with a commercially available two-dimensional focused geometry electronic detector. The detector is compact and portable, with unusually high spatial resolution comparable to that used in oscillation photography. It has allowed x-ray data collection on weakly diffracting crystals with large unit cells, as well as more conventional "diffractometer-quality" crystals. The quality of the data is compared with that from oscillation photography and automated diffractometry in the range of unit cells from 96.3 to 383.2 angstroms. Isomorphous and anomalous difference Pattersons, based on detector data, are shown for a variable surface glycoprotein mercury derivative and for a repressor-DNA bromine derivative, which has been solved at 7 angstroms with detector data only.     

Crystal Structure and Optical Properties of Cd32S14(SC6H5)36. DMF4, a Cluster with a 15 Angstrom CdS Core

Recrystallization of the solid Cd(10)S(4)(SC(6)H(5))(12) from a solution of pyridine and N, N-di-methylformamide (DMF) results in the formation of the cluster Cd(32)S(14)(SC(6)H(5))(36)-DMF(4) as pale yellow cubes. The structure consists of an 82-atom CdS core that is a roughly spherical piece of the cubic sphalerite lattice approximately 12 angstroms in diameter. The four corners of the lattice are capped by hexagonal wurtzite-like CdS units, which results in an overall tetrahedral cluster approximately 15 angstroms in diameter. This cluster dissolves intact in tetrahydrofuran where its absorption spectrum reveals a sharp peak at 358 nanometers at room temperature and its emission spectra show a strong broad band at 500 nanometers.