The $(n,\gamma )$ cross section of the unstable isotope ${}^{179}\mathrm{Ta}$ ${(t}_{1/2}=1.82\mathrm{}\pm 0.03\mathrm{yr})$ has been measured at thermal energies by means of the activation method. The ${}^{180}\mathrm{Hf}\mathrm{}(p,2n)\mathrm{}$ reaction was used for the production of ${}^{179}\mathrm{Ta},$and thin samples of 4 and 20 ng were obtained by the electrospraying technique. From irradiations with and without Cd absorbers the thermal cross section ${\sigma }_{\mathrm{th}}=932\mathrm{}\pm 62\mathrm{b}$ and the corresponding resonance integral $I_{\mathrm{res}}=1216\mathrm{}\pm 69\mathrm{b}$ could be determined.

• Received 16 March 1999

DOI:https://doi.org/10.1103/PhysRevC.60.025802