On the half-life of 44 Ti by results in meteorites

Measurements of the 44 Ti half-life display a large spread ranging from 46.4 to 66.6 years. The activity of this radioisotope measured in eight meteorites (chondrites) that fell in the time interval 1883-1992 and calculated at the time of fall by the different values of T ½ shows that the shorter values are not reliable, if it is assumed that the average cosmic-ray intensity has remained the same during the past two centuries. The low activity of the cosmogenic isotope 44 Ti has been determined by means of a selective Ge-NaI (Tl) γ-spectrometer with a very low background. The high stability of this system allows long-lasting runs (≡10 7 s), in order to achieve the standard deviation of counting up to 10%.