BETA(-LIFE OF MN-54 AND COSMIC-RAY CHRONOMETRY() DECAY PARTIAL HALF)

The weak beta(+) decay of the astrophysically significant radioisotope Mn-54 has been observed. The energies of positrons from a chemically purified Mn-54 source were measured using the APEX spectrometer at Arg onne National Laboratory. We deduce a beta(+) decay branch of (1.20 +/ - 0.26) X 10(-9), corresponding to a partial half-life of (7.1 +/- 1.5 ) x 10(8) yr. The implications of this value for cosmic-ray confinemen t times are discussed in light of recent satellite measurements of the cosmic-ray abundance of Mn-54.