Cosmic Radioactivity Research Articles

Study of the 26Al(n,p)26Mg and 26Al(n,α)23Na reactions using the 27Al(p,p')27Al inelastic scattering reaction

26Al was the first cosmic radioactivity ever detected in the galaxy as well as one of the first extinct radioactivity observed in refractory phases of meteorites. Its nucleosynthesis in massive stars is still uncertain mainly due to the lack of nuclear information concerning the 26Al(n,p)26Mg and 26 Al(n,α)23Na reactions. We report on a single and coincidence measurement of the 27Al(p,p')27Al(p)26Mg and 27Al(p,p')27Al(α)23Na reactions performed at the Orsay TANDEM facility aiming at the spectroscopy study of 27Al above the neutron threshold. Fourteen states are observed for the first time within 350 keV above the 26Al+n threshold.

Excited states above the proton threshold in 26Si

The level scheme above the proton threshold in 26Si is crucial for evaluating the 25Al(p, γ)26Si stellar reaction, which is important for understanding the astrophysical origin of the long-lived cosmic radioactivity 26Al(T 1/2 = 7.17 × 105 y) in the Galaxy. The excited states in 26Si have been studied using an in-beam γ-ray spectroscopy technique with the 24Mg(3He, nγ)26Si reaction. γ-rays with energies up to 4.6 MeV emitted from excited states in 26Si have been measured using large volume HPGe detectors. The spin-parity of one of the most important states reported recently at 5890.0keV has been assigned as 0+ by γ-γ angular correlation measurements in this work.

Astronomy with Radioactivities

Cosmic radioactivity represents a cross-disciplinary theme and an interesting alternate viewpoint on cosmic nuclear astrophysics. Radioactive isotopes and their decay provide unique messages from sites of cosmic nucleosynthesis, as the decay is mediated by weak interaction physics and independent of environmental conditions. The radioactive clock of various isotopes traces stellar mixing processes and the process of solidification of bodies when the solar system was formed. Isotopic abundances directly reflect the conditions of their formation in the nucleosynthesis site, which is unobservable otherwise. Measurements range from meteorites and their included stardust grain compositions through to cosmic rays and electromagnetic radiation from infrared to gamma ray wavelengths. Thus, various astronomical disciplines with their different messengers of cosmic nucleosynthesis as seen through unstable, decaying isotopes are linked to the physics of nuclear reactions, and to theories and models of the variety of cosmic nucleosynthesis sites and of cosmic isotopic evolution.

Cosmic Radioactivity and the Age of the Universe, 1900–1930

Cosmic Radioactivity and the Age of the Universe, 1900–1930

Formula omitted] atom counting for nuclear astrophysics

The nuclide 44 Ti (T 1/2=59.2 yr) has recently become an important asset to nuclear astrophysics through the measurement of its cosmic radioactivity, yielding significant information on fresh 44 Ti nucleosynthesis in supernovae. We propose to use AMS to determine the production rate of 44 Ti by the main channel believed to be responsible for 44 Ti astrophysical production, namely 40 Ca( α, γ ). A preliminary experiment conducted at the Koffler 14UD Pelletron accelerator demonstrates a sensitivity of 1×10 −14 for the 44 Ti/ Ti ratio. The AMS detection was performed using 44 Ti − ions sputtered from a TiO 2 sample, reducing considerably the 44 Ca isobaric interference. The present limit corresponds effectively to 44 Ti production with resonance strength in the range 10–100 meV for a one-day 40 Ca (α,γ) activation. Several such resonances are known to be responsible for 44 Ti production in the astrophysical temperature range and should be amenable to experiment with the proposed method.

Úvod do Radioaktivity

IT was in pitchblende from the mines of Jáchymov (St. Joachimsthal) in Bohemia that Prof, and Mme. Curie first discovered radium. The ores from these mines now yield radium preparations representing two to four grams of the pure element annually. In spite of the interest in the subject, the present volume is the first book by Czech men of science on radioactivity. It deals with the discovery and phenomena of radioactivity, the preparation of radium products and their physiological action, geophysics, cosmic radioactivity, and the technique followed at the Czech mines and extraction plant and at the Prague Radiological Institute. Úvod do Radioaktivity. Dr. F. Bêhounek Prof. Dr. J. Heyrovský. Pp. 116. (Praha: Jednoty Ĉs. Matematiku a Fysiku, 1931.) 24 Kĉ.