Observation of discrete energy electromagnetic emissions from celestial objects in the radio, IR, optical, lN, and X-ray spectral regions has dramatically advanced our know­ ledge in the field of astrophysics. It is expected that identification of nuclear 'Y-ray line emissions from any cosmic source would also prove to be a powerful new tool for probing the Universe. Since the publication of Morrison's work in 1958, many experiments were carried out searching for evidence of 'Y-ray lines from cosmic sources, however with little success. Only a few positive experimental results have been reported, in spite of an expenditure of considerable effort by many people: in particular, the possible Galactic Center emission line (473 to 530keV) and 'Y-ray lines at several energies (e. g. , 0. 5 MeV and 2. 2 MeV) associated with large solar flares. Both of these observations are unconfirmed by indepen­ dent observations (ca. 1975). The high energy 'Y-rays (>30MeV) from the Galactic Center are at least partly due to the decay of 1[0 mesons, which are of unique energy (67. 5 MeV) in the 1[0 rest frame only. The reasons for the limited amount of data avail­ able in this field, even though early theoretical predictions were very optimistic regarding fluxes of nuclear lines, are that experimental efforts are plagued with high backgrounds and low fluxes, and that development of instruments with telescopic properties in the energy range of interest is difficult.

Inhalt

I. Introduction.- 1.1. Brief History of Attempts to Detect Celestial ?-Rays 100 MeV).- e. Supernovae (Prompt Emission).- 3.2.2. Neutron Stars.- 3.2.3. Flare Stars.- 3.2.4. Galactic Core and Disk.- a. ?-Rays $$ \tilde > $$ 30 MeV.- b. 0.51 MeV Line Radiation.- c. ?-Ray Lines from Galactic Cosmic Rays.- 3.2.5. ?-Rays from Black Holes.- 3.2.6. Cosmic ?-Ray Bursts (Vela Class).- 3.3. Cosmic Diffuse Sources.- IV. Interaction of ?-Rays with Matter.- 4.1. ?-Ray Properties.- 4.2. Interaction Processes.- 4.2.1. Photoelectric Effect.- 4.2.2. The Compton Effect.- a. Polarized Incident Radiation.- b. Unpolarized Incident Radiation.- 4.2.3. Pair Production.- V. ?-Ray Flux Observations.- 5.1. Solar Observations.- 5.1.1. OSO-7 ?-Ray Observations in August 1972.- a. The August 4 event.- b. Time Profiles of the Positron Annihilation and Neutron Capture Lines - August 4 Event.- c. Preflare Upper Limits - August 4 Event.- d. Shape of the 0.5 MeV Line - August 4 Event.- e. ?-Ray Continuum - August 4 Event.- f. August 7 Event.- g. Conclusions Regarding Solar ?-Rays.- 5.2. Cosmic Observations (Point and Localized Sources).- 5.2.1. Supernovae and Supernova Remnants.- a. Supernova Remnants.- b. Supernovae.- 5.2.2. Galactic Disk and Center.- 5.2.3. Galactic Center ?-Ray lines.- 5.3. Diffuse ?-Ray Flux Observations (100 keV to 100 MeV).- 5.3.1. Observations (100 keV to 10 MeV).- 5.3.2. Observations (10 MeV to 100 MeV).- 5.4. Transient ?-Ray Bursts.- VI. Experimental Considerations for Nuclear ?-Ray Astronomy.- 6.1. Background Factors.- 6.1.1. Ambient Neutral Backgrounds.- a. The Diffuse ?-Ray Flux.- b. Atmospheric ?-Rays.- c. Intrinsic Activity.- d. Atmospheric Neutrons.- 6.1.2. Instrument Activation (Local Production).- 6.1.3. Satellite Orbits.- a. Intermediate Latitudes.- b. Polar Orbits.- 6.1.4. Space Probes.- 6.1.5. Observed Backgrounds in Specific Balloon Experiments.- a. Alkali Halide Spectrometers.- b. Solid State Detector Measurements.- c. Compton Telescope.- 6.2. Design Limitations.- 6.3. Current Detection Methods.- 6.3.1. Shielded Detectors.- a. HEAO-A Collimated X- and ?-Ray Spectrometer.- b. Collimator with Shutter-Occulter (Large ?-Ray Telescope).- c. Anti-Collimator Spectrometer.- d. HEAO-C Collimated Solid State Spectrometer.- 6.3.2. Compton Telescopes.- VII. Conclusions.- Notes Added in Proof.- Appendices.- A. Attenuation Coefficients for ?-Ray Interactions.- B. Conversion Factors for Energy Units.- References.