Disintegration ofGe68

The isotope ${\mathrm{Ge}}^{68}$ has been prepared by the bombardment of zinc with 37-Mev alpha particles and separated chemically. The half-life of ${\mathrm{Ge}}^{68}$ is 275±20 days, as determined by comparison with a ${\mathrm{Co}}^{60}$ standard over 10 months. The positron spectrum was measured with a thick-lens magnetic spectrometer. Positron groups from ${\mathrm{Ga}}^{68}$ have maximum energies of 1.94 and 0.92 Mev and relative intensities of 1 and 0.04, respectively; no positrons from ${\mathrm{Ge}}^{68}$ were observed above 0.3 Mev. The scintillation spectrum shows annihilation radiation and a 1.02-Mev gamma ray from ${\mathrm{Ga}}^{68}$. Comparison of areas under these two peaks, corrected for crystal efficiency, indicates that there are 14.4±1.7 positrons per 1-Mev quantum. Within the probable error, this result is compatible with the decay of ${\mathrm{Ge}}^{68}$ by electron capture alone.