Lifetime measurements andE2effective charges for nuclei in the1f72shell

Lifetimes for a number of levels in nuclei with $40<A<\mathrm{}56\mathrm{}$ have been measured using the recoil-distance technique. The experimental results for the mean lifetimes are ${45}_{-7\mathrm{}}^{+10\mathrm{}}$ psec for the 1491-keV $3^{+}$ and 57 ± 10 psec for the 1511-keV $5^{+}$ levels in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Sc}$; 8.1 ± 1.1 psec for the 2987-keV ${\frac{15}{2}}^{-}$ level in ${}_{}{}^{43}{}_{}{}^{}\mathrm{Sc}$; 19.6 ± 1.7 psec for the 3285-keV $6^{+}$ level in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$; 12.8 ± 1.2 psec for the 3334-keV $6^{+}$ level in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$; 5.1 ± 1.0 psec for the 1021-keV ${\frac{11}{2}}^{-}$ level in ${}_{}{}^{49}{}_{}{}^{}\mathrm{V}$; 12.6 ± 2.1 psec for the 783-keV $2^{+}$ level in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$; 20.4 ± 3.3 psec for the 238-keV ${\frac{7}{2}}^{-}$ level in ${}_{}{}^{51}{}_{}{}^{}\mathrm{Mn}$; ${13.7}_{-2.3\mathrm{}}^{+3.6\mathrm{}}$ psec for the 2369-keV $4_1^{+}$, 59.5 ± 3.3 psec for the 3114-keV $6^{+}$, and 10.4 ± 1.2 psec for the 3469-keV ($3^{\pm }$, $5^{-}$) levels in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$; 15.5 ± 1.8 psec for the 2563-keV ${\frac{13}{2}}^{-}$ and 3.9 ± 0.6 psec for the 2693-keV ${\frac{15}{2}}^{-}$ levels in ${}_{}{}^{53}{}_{}{}^{}\mathrm{Mn}$; and 5.7 ± 1.2 psec for the 2538-keV...