GALACTIC CONFINEMENT TIME OF IRON-GROUP COSMIC-RAYS DERIVED FROM THE MN-54 CHRONOMETER

Authors
ZAERPOOR K CHAN YD DIGREGORIO DE DRAGOWSKY MR HINDI MM ISAAC MCP KRANE KS LARIMER RM MACCHIAVELLI AO MACLEOD RW MIOCINOVIC P NORMAN EB
Citation
K. Zaerpoor et al., GALACTIC CONFINEMENT TIME OF IRON-GROUP COSMIC-RAYS DERIVED FROM THE MN-54 CHRONOMETER, Physical review letters, 79(22), 1997, pp. 4306-4309
Citations number
16
Journal title
Physical review letters → ACNP
ISSN journal
00319007
Volume
79
Issue
22
Year of publication
1997
Pages
4306 - 4309
Database
ISI
SICI code
0031-9007(1997)79:22<4306:GCTOIC>2.0.ZU;2-W
Abstract
The beta-decay half-life of Mn-54 is needed to employ this isotope as a cosmic ray chronometer. We have determined the partial half-life of Mn-54 for positron emission by counting a highly purified 35-mu Ci sou rce of Mn-54 in GAMMASPHERE to search for the astrophysically interest ing beta(+) decay branch through the observation of coincident positro n annihilation gamma rays. A careful analysis of 97 hours of source co unting and 61 hours of background shows a net signal of 24 +/- 10 back -to-back 511-511 keV coincident events. Based on this result, the bran ch for this decay mode is (2.2 +/- 0.9) x 10(-7)%. The implications of this result for the Mn-54 cosmic-ray chronometer problem are discusse d.