Nuclear Spectroscopy inCr52,Cr53, andCr54by the (p,d), (p,t), and (p,p′) Reactions

Abstract

The ${\mathrm{Cr}}^{54}\mathrm{}(p,d)\mathrm{}$ and ${\mathrm{Cr}}^{54}\mathrm{}(p,t)\mathrm{}$, ${\mathrm{Cr}}^{53}\mathrm{}(p,d)\mathrm{}$ and ($p,t$), ${\mathrm{Cr}}^{53}(p,p^{\prime })$, and ${\mathrm{Cr}}^{52}\mathrm{}(p,t)\mathrm{}$ reactions were studied with 17.5-MeV protons from the Princeton FM cyclotron. Thin, essentially self supported, isotopic chromium foils were used in these experiments, the deuterons and tritons being identified by a $\frac{\mathrm{dE}}{\mathrm{dx}}-E$ solid-state-detector telescope. The total experimental resolution of this system for the various deuteron and triton groups was between 55 and 70 keV. Angular distributions for many ($p,d$), ($p,t$), and ($p,p^{\prime }$) transitions were obtained from 15° to 150°. Spectroscopic factors were determined for $l_n=0,1,2,\mathrm{and} 3$ ($p,d$) transitions, using distorted-wave Born-approximation calculations which included both finite-range and nonlocal effects. In the ${\mathrm{Cr}}^{53}\mathrm{}(p,d)\mathrm{}$ reaction, both the $0^{+}$ ground state and the 1.434-MeV $2^{+}$ level in ${\mathrm{Cr}}^{52}$ were excited by $l_n=1\mathrm{}$ transitions, showing admixture in the ${\mathrm{Cr}}^{53}$ ground state of the configuration ${\left\{{\left({\mathrm{Cr}}^{52} 1.434 \mathrm{MeV}\right)}^{2^{+}}2p_{\frac{3}{2}}\right\}}^{\frac{3}{2}}$. Levels in ${\mathrm{Cr}}^{52}$ and ${\mathrm{Cr}}^{53}$ were strongly, excited in the ($p,d$) reaction with $l_n=3\mathrm{}$ angular distributions, and these transitions are ascribed to $1f_{\frac{7}{2}}$ pickup. In the ${\mathrm{Cr}}^{54}\mathrm{}(p,d)\mathrm{}{\mathrm{Cr}}^{53}$ reaction, definite $J$ dependence was observed in both $l_n=1\mathrm{}$ ($J=\frac{1}{2} or \frac{3}{2}$) and $l_n=3\mathrm{}$ ($J=\frac{5}{2} or \frac{7}{2}$) transitions. A single $l_n=0\mathrm{}$ transition was found in the ${\mathrm{Cr}}^{54}\mathrm{}(p,d)\mathrm{}$ reaction which seems to exhaust most of the $T_{<}$ spectroscopic strength. The ${\mathrm{Cr}}^{54,53,52}\mathrm{}(p,t)\mathrm{}$ experiments along with the ${\mathrm{Cr}}^{53}\mathrm{}(p,d)\mathrm{}$ work indicate that a large component of the 2.648-MeV $0^{+}$ level in ${\mathrm{Cr}}^{52}$ is a two-particle-two-hole neutron configuration. In the ${\mathrm{Cr}}^{53}(p,p^{\prime })$ reaction, the 0.563-MeV ${\mathrm{½}}^{-}$, 1.001-MeV ${\frac{5}{2}}^{-}$, 1.284-MeV ${\frac{7}{2}}^{-}$, and 1.967-MeV levels were strongly excited, and their angular distributions are similar to that of the ${\mathrm{Cr}}^{52}(p,p^{\prime }){\mathrm{Cr}}^{52}$ 1.434-MeV $2^{+}$ transition. The results of the ${\mathrm{Cr}}^{54}\mathrm{}(p,d)\mathrm{}$, ${\mathrm{Cr}}^{53}\mathrm{}(p,d)\mathrm{}$, and ${\mathrm{Cr}}^{53}(p,p^{\prime })$ experiments are used in conjunction with the weak-coupling model and the theoretical model calculations of Maxwell and Parkinson and of Ramavataram to discuss the structure of the low-lying levels of ${\mathrm{Cr}}^{53}$.