| Popis: |
The mean lifetimes of 15 excited states of ${\mathrm{Sc}}^{43}$ and upper and/or lower bounds for six others have been measured by the Doppler-shift attenuation method. The ${\mathrm{Ca}}^{40}(\ensuremath{\alpha},p\ensuremath{\gamma})$ and ${\mathrm{Ca}}^{42}\ensuremath{-}(p,\ensuremath{\gamma})$ reactions were used to populate the levels. For the ($\ensuremath{\alpha},p\ensuremath{\gamma}$) measurements, $\ensuremath{\gamma}$ rays were detected at 90\ifmmode^\circ\else\textdegree\fi{} to the $\ensuremath{\alpha}$-particle beam in coincidence with protons detected at + 110 and -110\ifmmode^\circ\else\textdegree\fi{}. The ${\mathrm{Sc}}^{43}$ ions were stopped in thick carbon backings, the stopping power of which is known from previous experimental work. For the ($p,\ensuremath{\gamma}$) measurements, $\ensuremath{\gamma}$ rays were detected at 0 and 135\ifmmode^\circ\else\textdegree\fi{} to the proton beam. The ${\mathrm{Sc}}^{43}$ ions were stopped in the target material. The results yield the following mean lives, in fsec (with the level energies in MeV given in parentheses): 230 \ifmmode\pm\else\textpm\fi{} 70 (0.846), g620 (0.856), 800 \ifmmode\pm\else\textpm\fi{} 300 (0.880), ${3100}_{\ensuremath{-}1200}^{+2700}(1.158)$, 400 \ifmmode\pm\else\textpm\fi{} 190 (1.179), 850 \ifmmode\pm\else\textpm\fi{} 250 (1.336), 240 \ifmmode\pm\else\textpm\fi{} 50 (1.410), 330 \ifmmode\pm\else\textpm\fi{} 100 (1.651), 22 \ifmmode\pm\else\textpm\fi{} 7 (1.810), 300 \ifmmode\pm\else\textpm\fi{} 50 (1.827), 80 \ifmmode\pm\else\textpm\fi{} 50 (1.885), g800 (1.930), 100 \ifmmode\pm\else\textpm\fi{} 20 (1.963), 410 \ifmmode\pm\else\textpm\fi{} 150 (2.094), 260 \ifmmode\pm\else\textpm\fi{} 70 (2.143), 150 \ifmmode\pm\else\textpm\fi{} 50 (2,580), 80 \ifmmode\pm\else\textpm\fi{} 20 (2.986), 5 (3.289), 10 (3.452), 5 (3.807), and 5 (4.455). The lifetime results for the 1.158- and 1.652-MeV levels are used to remove ambiguities in the measured mixing ratios. All results are compared with theoretical predictions of Johnstone and co-workers. |
