Isotopes in the interstellar medium and circumstellar envelopes

摘要: Measurements of the present-day abundances elements and isotopes, combined with model calculations, allow us to trace history nucleosynthesis in universe. Throughout this review, emphasis will be placed on descriptions measurement processes interpretations needed obtain actual isotope element from measurements. Comparisons isotopomers a given are less affected by systematic effects than comparisons different elements. Thus ratios should greater weight when data models compared. As is generally accepted, universe began an explosive event, Big Bang. The associated event produced `primordial' `light elements', deuterium, , . Subsequent stellar processing light has altered relative abundances, also heavier such as carbon, nitrogen oxygen. Stellar products solar larger mass stars expelled into interstellar medium (ISM). goal studies estimate primordial that is, It believed D always net destroyed stars; may produced, certainly produced. In Solar System itself, results obtained situ measurements space probes Jupiter, wind constituents, analysis content meteorites, spectral line photosphere. For sources outside System, these based gas-phase species. ratio elements, carbon lithium differing amounts condensation onto dust grains; however process not affect isotopes most reliable H spectroscopic Lyman series ultraviolet absorption lines foreground gas. clouds our galaxy have been satellites International Ultraviolet Observatory, Copernicus, Hubble Space Telescope. interesting new development distant large redshifted velocities. Such can taken Earth-bound optical telescopes. near future Far Ultra Violet Explorer refine extend D/H relatively nearby regions. Abundances ISM measured using hyperfine transition galactic II regions which ionized high-mass stars. abundant abundance must very accurately determined if one wishes use quantity baryon density early Recently /H number metal-poor compact blue galaxies. These seem had little evolution, so close value. Estimates made for population old found far plane galaxy. A refinement Li estimates requires more detailed understanding destruction