Production of high-spin isomers in proton induced reactions at $100–500\text{MeV}$ on ${}^{181}\mathrm{Ta}$

Cross sections for production of a broad variety of high-spin isomers, i.e., ${}^{177}{\mathrm{Hf}}^{m2}\left(37∕2^{-}\right)$, ${}^{179}{\mathrm{Hf}}^{m2}\left(25∕2^{-}\right)$, ${}^{177}{\mathrm{Lu}}^m\left(23∕2^{-}\right)$, ${}^{180}{\mathrm{Hf}}^m\left(8^{-}\right)$, and ${}^{178}{\mathrm{Ta}}^m\left(7^{-}\right)$ from ${}^{181}\mathrm{Ta}$ targets irradiated with 100, 145, 200, 350, and $500\text{MeV}$ protons have been measured by off-line $\gamma$-spectroscopy. A radiochemical procedure was used to achieve high sensitivity. Isomer ratios in products ranging down to ${10}^{-3}$ were based on experimentally measured and theoretically calculated cross sections. It was demonstrated that the isomer ratio does not depend essentially on proton energy in the given range. Regularities in formation of isomeric states in different nuclear reactions are discussed.

Figure 1

$\gamma$-spectrum of analytical line of ${}^{177}{\mathrm{Hf}}^{m2}$ (spin $37∕2^{-}$) after chemical separation. Data for different decay periods after the end of bombardment (EOB) by $100\text{−}\text{MeV}$ protons are shown.

Figure 2

The experimental results of this work for isomer production cross section.

Figure 3

Excitation function for the ${}^{181}\mathrm{Ta}(p,2p10n)$ ${}^{170}\mathrm{Hf}$ (top panel) and ${}^{181}\mathrm{Ta}(p,3p10n)$ ${}^{169}\mathrm{Lu}$ (bottom panel) reactions. The experimental result of this work (O) is compared with two theoretical predictions: CEF (solid curve) and ALICE (dashed curve) codes; (□) Asano et al. [17], ($▵$) Neidhart et al. [18].

Figure 4

Isomer ratio dependence on incident proton energy; (O), ${}^{178}{\mathrm{Ta}}^m;$ (◇), ${}^{180}{\mathrm{Hf}}^m$; (□), ${}^{177}{\mathrm{Lu}}^m$; $(▵)$, ${}^{179}{\mathrm{Hf}}^{m2}$; $(\times )$, ${}^{177}{\mathrm{Hf}}^{m2}$.

Figure 5

Isomer ratio dependence on isomer spin at $100\text{MeV}$.