High spin states in the two nuclei ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Mn}$, with $J^{\pi }$≤${11}^{+}$, have been studied via the reactions ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$(α,p2nγ) and ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$(α,3nγ), respectively, by in-beam γ-ray spectroscopy. Measurements of lifetimes of excited states by the Doppler shift attenuation and recoil distance techniques, γ-ray angular distributions, excitation functions, and γγ coincidence, have been carried out in both the nuclei. New results obtained in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ are the mean lifetime values of ${0.35}_{\mathrm{-}0.13}^{+0.25\mathrm{}}$, ${0.23}_{\mathrm{-}0.11}^{+0.22\mathrm{}}$, and <2.0 ps for the three highest observed states 8216.0 (${11}^{+}$), 7237.1 (${10}^{+}$), and 6453.4 keV ($9^{+}$), and multipole mixing ratios ${\mathrm{-}0.10}_{\mathrm{-}0.05}^{+0.08\mathrm{}}$, ${0.06}_{\mathrm{-}0.03}^{+0.05\mathrm{}}$, and ${\mathrm{-}0.22}_{\mathrm{-}0.15}^{+0.08\mathrm{}}$ for the 978.9, 784.7, and 629.1 keV γ rays depopulating these states, respectively. In ${}_{}{}^{52}{}_{}{}^{}\mathrm{Mn}$, the lifetime of the 4163.4 keV (${10}^{+}$) state, hitherto unreported, has been measured to be ${0.20}_{\mathrm{-}0.16}^{+0.35\mathrm{}}$ ps.

Lifetimes of two other states in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Mn}$, at 870.1 ($7^{+}$) and 2907.9 keV ($9^{+}$), for which only the upper limits were known previously, have been measured in this work and are found to be ${0.07}_{\mathrm{-}0.04}^{+0.08\mathrm{}}$ and 0.12±0.08 ps, respectively. A comparison of the present experimental results on level lifetimes, multipole mixing ratios, and transition probabilities with the available theoretical calculations shows that most of the levels in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ with excitation energies greater than 3.4 MeV are almost pure 1p5h states, while the lower lying states have a predominantly 0p4h configuration, with ∼20% 1p5h admixture. The observed M1 and E2 transition strengths between the high spin states in ${}_{}{}^{52}{}_{}{}^{}\mathrm{Mn}$ favor interpretation of these states as having predominantly ($f_{7/2}$${)}^n$ configuration and provide evidence for the existence of collective features in this nucleus.

• Received 7 April 1987

DOI:https://doi.org/10.1103/PhysRevC.36.2274