The 238U(n, α)235Th reaction with thermal neutrons

The thermal neutron induced (n, α) reaction cross section of ²³⁸U was measured using the highly pure thermal neutron beam from the 87 m curved neutron guide at the High Flux Reactor of the ILL (Grenoble). The energy spectrum showed an α-particle line with E_α = 9.05±0.06 MeV and σ(n, α) = 1.3±0.6 μb. The α-particle energy was used to calculate the ²³⁵Th mass of 235.04700±0.00008 amu, the Q_α value of 9.20±0.06 MeV for the ${}^{238}\text{U(n}\text{, α)}{}^{235}\text{Th}$ reaction and the Q_β value of 1.44±0.08 MeV for the β-decay of ²³⁵Th. The cross-section data are compared with the results obtained with the statistical model calculation.