Maria C. Perillo Isaac

Influence of physical and chemical environments on the decay rates of 7Be and 40K

We measured the electron-capture decay rate of 7Be implanted into hosts of graphite, boron nitride, tantalum, and gold. We have found that this decay rate varies by as much as 0.38% from one host to another. We also measured the electron-capture decay rate of 40K in four different chemical compounds and as both a solid and dissolved in solution. To within our measurement precision of ±1%, we have found no influence of the environment on the 40K decay rate. The implications of these results for the solar neutrino problem and for potassium/argon dating are discussed.

Search for Strange Matter by Heavy Ion Activation

We present the results of an experimental search for stable strange matter using the heavy ion technique, based on properties of strangelets. We studied samples of a meteorite, terrestrial nickel ore, and lunar soil. Our search improved by 2 to 3 orders of magnitude the existing experimental limit on the strange matter content in normal matter and enabled probing the flux of low mass strangelets on the lunar surface for the first time.p {copyright} {ital 1998} {ital The American Physical Society}

Cosmic-ray history derived from the 54Mn, 56Ni and 144Pm chronometers

Sources of 54 Mn, 55 Ni, and 144 Pm were placed at the center of the Gammasphere array and searches were made for the astrophysically interesting β + decay modes of these isotopes. The results of these searches are presented and the implications for cosmic-ray physics are discussed.