First observation of inelastic X-ray scattering from condensed ⁴He using high energy resolution

Recently, the suitability of inelastic X-ray scattering for the investigation of solid and fluid ⁴HE has been demonstraded. For the text experiments an energy resolution of the order of 10-15 meV was used at the backscattering spectrometer INELAX at the storage ring DORIS of DESY, Hamburg. Lattice excitations were observed for momentum transfers along the c axis of h.c.p. helium crystals which were grown in situ at pressures of 54-63 Mpa and at temperatures of 4.2-6.4 K. At 10 k abowve the melting point, engery-loss signals could also be detected from the liquid helium at equivalent momentum transfers.