Cross Section of Slow Neutrons on Parahydrogen

The total cross section for interaction of slow neutrons by parahydrogen has been measured to 0.1%. A pressure dependence has been found whose origin is obscure. By extrapolation to $p=0\mathrm{}$, a value for the coherent scattering length of (-3.707±0.008) × ${10}^{-13\mathrm{}}$ cm is found, in agreement with the liquid-mirror result of (-3.721±0.004) × ${10}^{-13\mathrm{}}$ cm.