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

Measurements of the 44Ti half-life display a large spread ranging from 46.4 to 66.6 years. The activity of this radioisotope measured in eight meteorites (chondrites) fell in the time interval 1883-1992 and calculated at the time of fall by the different values of T1O2 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 44Ti has been determined by means of a selective Ge-NaI (Tl) g-spectrometer with a very low background (about 1 count per day in the g-peak at 1157 keV of 44Sc in equilibrium with its parent 44Ti). The high stability of this system allows long-lasting runs (A107 s ), in order to achieve the standard deviation of counting up to A10%. PACS 94.40.Vf – Cosmic-ray effects in meteorites and terrestrial matter