Mean Lifetimes of the First Excited States ofLi7andNa23by Reson

Abstract

A 1.4-MeV electron accelerator was used as a source of bremsstrahlung to determine the widths T, and, hence, the mean lifetimes r, of the first excited states of Li 7 and Na 23 . Self-absorption experiments were performed in both cases. For the 480-keV level in Li 7 the following results were obtained: T= (5.28±0.27) X10 -3 eV, corresponding to r= (1.25±0.06)X10-13 sec. For the 440-keV level in Na 23 the results obtained were r= (3.66±0.50)XH)-4 eV, corresponding to r= (1.80db0.28)X10-12 sec.