New Isotopes fromK78rFragmentation and the Ending Point of the Astrophysical Rapid-Proton-Capture Process

Abstract

In an experiment at the SISSI/LISE facility of GANIL, we used the projectile fragmentation of a "Kr primary beam at 73 MeV/nucleon to produce new isotopes of astrophysical interest. We obtained clear evidence for the existence of the five new isotopes Ga, 4As, Kr, and ' Sr. However, we did not find any evidence for Br, whereas comparable nuclei were observed with more than 1000 counts. The isotope 9Br is thus deduced to be a proton-unbound nucleus with a half-life shorter than about 100 ns.

Decay of proton-rich nuclei between 39Ti and 49Ni

“…The observation of nuclei very close to this limit of existence was possible due to recent developments of projectile fragmentation facilities. Indeed, in the mass region we are interested in here, a recent experiment at the GSI/FRS facility allowed for the observation of 42 Cr (T z = −3) as well as of 45 Fe and 49 Ni (T z = −7/2) [1]. During an experiment at the GANIL/LISE3 separator, the existence of these isotopes has been confirmed with increased statistics and 48 Ni has been observed for the first time [2].…”

“…Some information, like rough lifetime estimates and a few delayed proton lines, is also available for 43 Cr, 46 Mn and 46,47 Fe [19]. For the most exotic isotopes, 42 Cr, 45 Fe and 49 Ni, only their existence was reported [1].…”

Synthesis of the elements in stars: forty years of progress

“…At the upper end of their temperature range significant abundances of 74 Se and 78 Kr could be produced. However, 69 Br, which might be thought to be formed by 68 Se(p,␥) 69 Br, was subsequently found to be proton unbound (Blank et al, 1995). Since the half-life of 68 Se is 35.5 s, appreciably longer than the highest temperature conditions can persist, the rp process will be slowed appreciably at mass 68.…”

“…One important consequence of the Hot CNO cycle is the production of an ͓ 15 N/ 14 N] isotope ratio of ϳ1 (compared to the ratio of ϳ4ϫ10 Ϫ5 produced in the CNO cycle), indicating that in the solar system (͓ 15 N/ 14 N]Ϸ4ϫ10 Ϫ3 ) most of the observed 15 N was produced in nova explosions. At still higher temperatures, the reaction sequence 15 O(␣,␥) 19 Ne(p,␥) 20 Na may provide a breakout path from the Hot CNO Cycle to the rp process (Wallace and Woosley, 1981), which can provide contributions to the nucleosynthesis of proton rich isotopes up through 65 As (e.g., Mohar et al, 1991), to as high as 68 Se (e.g., Blank et al, 1995), or even to 96 Ru (Schatz et al, 1997).…”

“…Finally, the decay modes may be important as, e.g., ␤ ϩ decay and ␤ ϩ -p decay will produce different final nuclides from the ␥ process. Thus significant effort has gone into observing these properties of the very proton-rich nuclides (Boyd, 1994;Winger et al, 1993;Blank et al, 1995).…”