NEUTRON RESONANCES OF MO ISOTOPES

The neutron transmission of Mo isotopes for neutron energy En 1.5 keV has been measured with the Argonne fast chopper. The use of samples enriched in Mo95 and in Mo97 as well as samples of natural Mo has made possible the unambiguous isotopic assignment of the resonances. Some ten new resonances have been detected and measured; all of these have been assigned to either Mo95 or Mo97. On the basis of a probability approach recently suggested by Bollinger, a great majority of these newly observed resonances have been interpreted as being due to p-wave neutrons. For Mo95 the mean radiation width calculated from the measurements for the resonances at E0=44.7and159.6 eV is l=0=185±15 meV. This is to be compared with l=1=277±67 meV for the two p-wave resonances at E0=110.3and117.9 eV. For Mo96, the widths are l=0=330±50 meV for the resonance at 131.3 eV, and (Γγ)l=1=530±100 meV for the resonance at E0=113.5 eV. For Mo97, the radiation widths are (Γγ)l=0=127±13 meV for the s-wave resonance at E0=70.9 eV, and l=1=154±20 meV for four of the p-wave resonances detected in this experiment. The values for Mo98 are (Γγ)l=0=170±80 meV for the s-wave resonance at E0=428.9 eV, and (Γγ)l=1=110±15 meV for the p-wave resonance at E0=12.1 eV. The strength functions calculated for these nuclides are S0(Mo95)=(0.5-0.2+0.5)×10-4, S1(Mo95)=(5-3+10)×10-4; S0(Mo97)=(0.5-0.2+0.4)×10-4, S1(Mo97)=(6-2+11)×10-4; and S0(Mo98)=(2-1+4)×10-4. The resonance-capture integral for natural Mo has been calculated to be 27±2 b. © 1969 The American Physical Society.