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Laboratory astrophysics under the ultraviolet, visible, and gravitational astrophysics research program: oscillator strengths for ultraviolet atomic transitions
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Federman, Steven R. |
| Copyright Year | 1992 |
| Description | The conditions within astrophysical environments can be derived from observational data on atomic and molecular lines. For instance, the density and temperature of the gas are obtained from relative populations among energy levels. Information on populations comes about only when the correspondence between line strength and abundance is well determined. The conversion from line strength to abundance involves knowledge of meanlives and oscillator strengths. For many ultraviolet atomic transitions, unfortunately, the necessary data are either relatively imprecise or not available. Because of the need for more and better atomic oscillator strengths, our program was initiated. Through beam-foil spectroscopy, meanlives of ultraviolet atomic transitions are studied. In this technique, a nearly isotopically pure ion beam of the desired element is accelerated. The beam passes through a thin carbon foil (2 mg/cu cm), where neutralization, ionization, and excitation take place. The dominant process depends on the energy of the beam. Upon exiting the foil, the decay of excited states is monitored via single-photon-counting techniques. The resulting decay curve yields a meanlife. The oscillator strength is easily obtained from the meanlife when no other decay channels are presented. When other channels are present, additional measurements or theoretical calculations are performed in order to extract an oscillator strength. During the past year, three atomic systems have been studied experimentally and/or theoretically; they are Ar, I, Cl I, and N II. The results for the first two are important for studies of interstellar space, while the work on N II bears on processes occurring in planetary atmospheres. |
| File Size | 542039 |
| Page Count | 14 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19920010971 |
| Archival Resource Key | ark:/13960/t0sr3sk75 |
| Language | English |
| Publisher Date | 1992-02-29 |
| Access Restriction | Open |
| Subject Keyword | Astrophysics Planetary Atmospheres Spectroscopy Gravitation Populations Energy Levels Molecular Spectra Atoms Electron Transitions Gas Temperature Carbon Ion Beams Interstellar Space Foils Materials Ionization Oscillator Strengths Extraction Excitation Line Spectra Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
