Effect of theλTransition on the Atomic Distribution in Liquid Helium by Neutron Diffraction

Neutron diffraction patterns for samples of liquid helium at 1. 06^, 2. 29^, and 2. 46^ have been measured over the angular range 4^ to 64^ using 1. 06₄ A neutrons. The liquid structure factor i (s) +1 was deduced for each curve and these show a change which is associated with the transition which indicates that the spatial order in the liquid is smaller below the point than above. The measurements were transformed to give the radial distribution function 4r^2 (r) -₀ from which was deduced the number of neighbors under the first shell of atoms and the nearest distance of approach of two atoms in the liquid. These lie between 8. ₅ atoms and 9. ₈ atoms and 2. 35 A and 2. 40 A, respectively.