Identification of [Fe III] in the solar ultraviolet spectrum
Solar ultraviolet spectra have been obtained with high spectral and spatial resolution using the Naval Research Laboratory's high-resolution telescope and spectrograph1 (HRTS) flown on rockets since 1975 and most recently on the Spacelab 2 Shuttle flight. Because the solar spectrum between ∼1,170 and 1,719 Å has been well observed for some years, few lines of substantial intensity remain unidentified. (See for example the recent compilation by Sandlin et al.2). The longest exposures during the first rocket flight of the HRTS, which obtained spectra with a spatial resolution of ∼ 1 arc s along the slit, of length ∼ 1 solar radius, and a spectral resolution of ∼0.05 Å, showed a number of weak emission lines at the solar limb, in particular between 1,570 and 1,600 Å (see Plates 16 and 17 in ref. 3), that could not readily be identified. Improved observations of these lines were obtained during the flight of HRTS on the Spacelab 2 Shuttle flight in July–August 1985, by making longer exposures (60,100 and 250 s). The scope of the data obtained has been described4. We have now identified the emission lines concerned as forbidden (electric quadrupole and magnetic dipole) transitions in Fe III, the first detection of these particular transitions in any source. They must now be considered potential candidates for previously unidentified lines in other low-density (Ne ≲ 1010 cm−3) astrophysical sources.
Narrow and variable lines in the ultraviolet spectrum of the Seyfert galaxy NGC4151
The Seyfert galaxy NGC4151 observed when the nucleus is at a minimum has two emission lines of full width at half maximum <7 and 16 Å respectively and varying in intensity by a factor of three in 10 days. These lines are too narrow to be emitted by the whole broad-line region and must arise instead from two localized regions which have a special excitation mechanism, possibly a two-sided jet.
Physical Processes in Inorganic Scintillators
BASIC PRINCIPLES AND PROCESSES Physical Mechanism of Scintillation Creation of Electron Hole Pairs Excitation and Emission of Luminescence Centers Scintillation Materials Halides Oxides and Oxide Systems Chalcogenides Glasses Interaction of Ionizing Radiation with Scintillators High Energy Photons Charged Particles Neutral Particles General Characteristics of Inorganic Scintillators Light Yield Duration of Scintillation Pulse Afterglow Temperature Response Optical Properties Radiation Hardness Density Emission Spectra Mechanical and Chemical Properties Physical Parameters Cost Consideration Scintillator Requirements in Various Applications High Energy Physics Intermediate Energy Physics Positron Emission Tomography Gamma Spectroscopy Energy Resolution Intrinsic Scintillator Resolution Nonproportional Response Time Resolution Low Energy Quanta and Electrons CONVERSION OF ELECTRONIC EXCITATIONS IN SOLIDS Charge Carrier Behaviors Delta Rays Secondaries Excitation of Luminescence Centers Effect of Ionization Density Energy Losses Simple Phenomenological Model Plasmon Model Polaron Model Scintillation Yield Spectra Vacuum Ultraviolet Region Ultrasoft X-Rays X-Rays Gamma Rays Heavy Ionizing Particles INTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Excitonic Luminescence Alkali Halide Crystals Alkaline-Earth Fluorides Ternary Halide Compounds Excitonic-Like Luminescence Cesium Iodide Tungstate and Molybdate Phosphors Core-to-Valence Transitions First Evidence for Radiative Core-to-Valence Transitions Excitation Spectra Emission Spectra Experiment Theory Luminescence Kinetics Experimental Theoretical Investigations Temperature Dependence of Luminescence Parameters Conditions of Detection Prospects for Research EXTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Thallium-Activated Halide Scintillators Crystals with NaCl-Type Structure Crystals with CsCl-Type Structure Other Thallium-Based and Thallium-Doped Crystals Crystals Containing Other ns2 Ions Bismuth Germanate (BGO) Sodium-Activated Cesium Iodide Rare-Earth-Activated Crystals General Considerations Europium-Activated Crystals Cerium-Activated Compounds Preliminary Comments LaF3-CeF3 Systems Cerium Chloride Barium Fluoride Gadolinium-Containing Crystals Lu- and Y-Containing Crystals Nd- and Pr-Activated Crystals DEFECT FORMATION BY IONIZING RADIATION Effect on Scintillator Characteristics Mechanisms of Defect Formation Efficiency of Defect Production Geometrical Factor Separation between F and H Centers Temperature Dependence of Production Efficiency Role of Halogen Ion Impurities Effect of Cation Impurities Formation Time of F-H Pairs Closing Comments References Index