Geophysical determination of the La-138 beta(-) decay constant - art. no. 017601

The La-138 beta- decay constant was determined geophysically. The isotopic growths of Ce-138/Ce-142 and Nd-143/Nd-144 were examined from ancient igneo us crystalline rocks. For the Ce isotope measurement, a newly developed dyn amic multicollector technique was applied. The crystallization age of the r ocks was calculated to be 2037+/-13 Myr from the growth of Nd-143. From the age and the growth of Ce-138, lambda(beta) of La-138 was estimated to be ( 2.37+/-0.10) x 10(-12) yr(-1). This value is consistent with those of the l atest two gamma-ray counting data of lanthanum compounds within the analyti cal error.