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 $4^{+}$ level in ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$. Lifetime limits were found for eight additional levels in these nuclei. In addition, an improved value $\tau =68.3\mathrm{}\pm 3.1$ psec was obtained for 937-keV $3^{+}$ level in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$. The $B\left(E2\mathrm{}\right)\mathrm{}$ strengths for transitions in nuclei with $42\le A\le 44$ are collected and interpreted in terms of isospin-dependent effective charges using wave functions for the ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^n$, and ${\mathrm{}\left(\mathrm{fp}\right)\mathrm{}}^n$, and ${\mathrm{}\left(\mathrm{fp}\right)\mathrm{}}^{n+m}{\mathrm{}\left(\mathrm{sd}\right)\mathrm{}}^{-m}$ model spaces. The core-polarization charges obtained from an analysis using ${\mathrm{}\left(\mathrm{fp}\right)\mathrm{}}^2+{\mathrm{}\left(\mathrm{fp}\right)\mathrm{}}^4{\mathrm{}\left(\mathrm{sd}\right)\mathrm{}}^{-2\mathrm{}}$ wave functions are $e_p=1.16\mathrm{}\pm 0.16$ and $e_n=0.45\mathrm{}\pm 0.03$. Core-deformation effects are found to enhance the isoscalar but not the isovector effective charges for states with low spin. The $B\left(E2\mathrm{}\right)\mathrm{}$ strengths for transitions in the isotones with 28 neutrons are also collected and interpreted using ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^n$ wave functions. The effective proton charge is found to be approximately constant for all transitions with $e_p=1.8-2.0\mathrm{}$. Estimates of effective proton charges for these nuclei resulting from the use of larger model spaces are discussed allowing an approximate comparison for the whole $40<A<\mathrm{}56\mathrm{}$ region.

[NUCLEAR REACTIONS ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}(\alpha ,n) E=10.4\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^3{}_{}{}^{}\mathrm{He},p) E=10.5\mathrm{}$ MeV, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({}_{}{}^3{}_{}{}^{}\mathrm{He},p) E=10.5\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\alpha ,p) E=14.0\mathrm{}$ MeV, ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}(\alpha ,p) E=14.0\mathrm{}$ MeV, ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}(\alpha ,p) E=10.0\mathrm{}$ MeV, ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}(\alpha ,p) E=11.0\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},\alpha 2p) E=47\mathrm{}$ MeV, ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}(\alpha ,n) E=14.5\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},3p) E=47\mathrm{}$ MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},2p) E=47\mathrm{}$ MeV; measured recoil distance. Deduced $T_{\frac{1}{2}}$, $B\left(E2\mathrm{}\right)\mathrm{}$. Deduced $40<A<\mathrm{}56\mathrm{}$ effective charges. Natural and enriched targets, Ge(Li) detector.]

• Received 5 October 1973

DOI:https://doi.org/10.1103/PhysRevC.9.1033