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 ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(p,\gamma ){}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ reaction, and the Doppler-shift attenuation technique, 18 ± 6 fsec is found for the mean life of the $6^{+}$ state. It follows that the strength of the $6^{+}$ → $4^{+}$ 3926-keV transition is 9.4 ± 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 $6^{+}$ → $4^{+}$ transition strength.