Two-dimensional pulse height and time-of-flight (TOF) spectra were measured at the IBR-30 pulsed neutron source to make the isotopic identification of the parity-violating $p$-wave resonance at $E_0=3.2\mathrm{}$ eV recently observed in Xe. Analysis of the TOF spectra corresponding to the characteristic low-energy gamma-rays established the ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ isotope as the origin of the 3.2-eV resonance. This new finding poses a challenge for the development of a polarized solid ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ target for a test of time-reversal invariance with neutrons.

• Received 18 March 1996

DOI:https://doi.org/10.1103/PhysRevC.53.R2573