8543-keV6+State inSi28and the Ground-State Rotational Band

Abstract

Evidence for the existence of a ground-state rotational band in the nucleus $^{28}\mathrm{Si}$ has been rounded out by a lifetime measurement of the 8543-keV ${6}^{+}$ level. Using the 2203-keV resonance in the $^{27}\mathrm{Al}(p,\ensuremath{\gamma})^{28}\mathrm{Si}$ reaction, and the Doppler-shift attenuation technique, 18 \ifmmode\pm\else\textpm\fi{} 6 fsec is found for the mean life of the ${6}^{+}$ state. It follows that the strength of the ${6}^{+}$ \ensuremath{\rightarrow} ${4}^{+}$ 3926-keV transition is 9.4 \ifmmode\pm\else\textpm\fi{} 3.0 Weisskopf units (W.u.), in good agreement with theoretical predictions. This measurement removes objections that arose from an earlier result of 2.9 W.u. for the ${6}^{+}$ \ensuremath{\rightarrow} ${4}^{+}$ transition strength.