Formation of the isomeric pair ${}^{194}$Ir${}^{m,g}$ in interactions of $\alpha$ particles with ${}^{192}$Os

Cross sections were measured by the activation technique for the nuclear processes ${}^{192}$Os(α,$d$+$\mathit{pn}$+$\mathit{np}$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$ up to α-particle energies of 39 MeV. From the measured data the isomeric cross-section ratio was deduced as a function of projectile energy. The present experimental data as well as those for the ${}^{194}$Pt($n$,$p$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$ reaction, given in the literature, were compared with the results of nuclear model calculations using the code talys, which combines the statistical, precompound, and direct interactions. In general, the experimental data were reproduced well by the model calculations, which were done using relatively low values of η (i.e., ${\Theta }_{\mathrm{eff}}/{\Theta }_{\mathrm{rigid}}$). The results provide more evidence for the mass dependence of η. The level density parameter for ${}^{194}$Ir was determined unambiguously.

Figure 1

Decrease in the count rate of the 328.45-keV γ ray as a function of decay time. The data were fitted with the known half-lives of the two independently decaying isomeric states ${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$.

Figure 2

Measured and calculated excitation function of the ${}^{192}$Os(α,$d$+$\mathit{pn}$+$\mathit{np}$)${}^{194}$Ir${}^g$ process.

Figure 3

Measured and calculated excitation function of the ${}^{192}$Os(α,$d$ $+$ $\mathit{pn}$ $+$ $\mathit{np}$)${}^{194}$Ir${}^m$ process.

Figure 4

Measured and calculated isomeric cross-section ratios of the ${}^{192}$Os(α,$d$ $+$ $\mathit{pn}$ $+$ $\mathit{np}$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$ processes with the best $\eta$ $=$ 0.275 value, as well as with $\eta$ $=$ 0.20 and $\eta$ $=$ 0.40.

Figure 5

Measured and calculated excitation function of the ${}^{194}$Pt($n$,$p$)${}^{194}$Ir${}^g$ reaction. The measured data were taken from the literature (Filatenkov and Chuvaev [13], Coleman et al. [25], Hankla et al. [26], Molla and Qaim [27], Hua et al. [28]), and the result of nuclear model calculation (talys) is from this work.

Figure 6

Measured and calculated excitation function of the ${}^{194}$Pt($n$,$p$)${}^{194}$Ir${}^m$ reaction. The measured data are from Filatenkov and Chuvaev [13] and the result of nuclear model calculation is from this work.

Figure 7

Measured and calculated isomeric cross-section ratios of the ${}^{194}$Pt($n$,$p$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$ reactions. The measured data are from Filatenkov and Chuvaev [13] and the result of nuclear model calculation is from this work.

Figure 8

The “reduced” ${\chi }^2$value as a function of the $\eta$ value used for the calculation of the isomeric cross-section ratio in the reactions ${}^{192}$Os(α,$d$ $+$ $\mathit{pn}$ $+$ $\mathit{np}$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$ and ${}^{194}$Pt($n$,$p$)${}^{194}$Ir${}^m$${}^{,\mathrm{g}}$.