Cross sections of 151Eu(n,2n)150mEu and 159Tb(n,2n)158Tb reactions near their thresholds

Cross sections were measured for the first time for the formation of long-lived products ${}^{\mathrm{<mtext>150</mtext><mtext>m</mtext>}}\text{Eu}\text{(T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 35.8}\text{y}\text{)}\text{and}{}^{158}\text{Tb}\text{(T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 180}\text{y}\text{)}$ in (n,2n) reactions on ¹⁵¹Eu and ¹⁵⁹Tb, respectively, over the neutron energy range of 8.7–10.7 MeV. The quasi-monoenergetic neutrons were produced via the ²H(d,n)³He reaction using a deuterium gas target at a variable energy compact cyclotron. Use was made of the activation technique in combination with high resolution γ-ray spectroscopy. The transition from the present low energy data to the available cross section values around 14 MeV appears to be smooth.