NUCLEAR STRUCTURE OF NA22 .V. DOPPLER-SHIFT ATTENUATION MEASUREMENTS

The mean lifetimes of seven nuclear levels of Na22 have been measured by the Doppler-shift attenuation method. The F19(α,n)Na22 reaction was used to populate the levels. γ rays were observed at 0°to the α beam with a Ge(Li) detector. The results, when averaged with previous work, yield the following mean lives (in psec) for the indicated levels: 0.891 (12.25±1.75), 1.528 (3.5±0.6), 1.984 (1.74±0.34), 2.211 (20-8+25), 2.572 (5.7±0.9), 2.969 (0.060±0.013), and 3.059 (0.040±0.01), where the levels are designated by their excitation energies (in MeV). For the five lowest levels the lifetimes were obtained from an analysis of Doppler-shifted line shapes; the remaining two lifetimes were determined from conventional centroid-shift analysis. The latter method also gave a lifetime of 5.2±0.9 psec for the 1.346-MeV level of F19. Some information was obtained on the M2E1 mixing ratios of the ground-state and first-excited-state transitions from the Jπ=2-A 2.572-MeV level of Na22. Evidence for a K=1 odd-parity rotational band in Na22 is discussed. © 1968 The American Physical Society.