Lifetime of theBe103.37-MeV Level. I. Experiment

Collective effects in $E2\mathrm{}$ transitions are found even in light nuclei. We have sought to extend the knowledge of this phenomenon by measuring the lifetime of the $2^{+}$ first excited state of ${\mathrm{Be}}^{10}$ at 3.37 MeV. To do this we have used two new variants of the Doppler-shift attenuation method. The ${\mathrm{Be}}^{10}$ was produced by the ${\mathrm{Be}}^9\mathrm{}(d,p)\mathrm{}{\mathrm{Be}}^{10}$ reaction and the recoiling ${\mathrm{Be}}^{10}$ was slowed down in beryllium or in beryllium-copper. We find a mean lifetime of (1.4±0.3)×${10}^{-13\mathrm{}}$ sec. The analysis of Doppler-shift measurements of the type used here is given at length.