We have developed a matter wave interferometer based on the diffraction of atoms from effective absorption gratings of light. In a setup with cold rubidium atoms in an atomic fountain the interferometer has been used to carry out tests of the equivalence principle on an atomic basis. The gravitational acceleration of the two isotopes 85 Rb and 87 Rb was compared, yielding a difference ∆g/g = (1.2 ± 1.7) · 10 −7 . We also perform a differential free fall measurement of atoms in two different hyperfine states, and obtained a result of ∆g/g = (0.4 ± 1.2) · 10 −7 .

No abstract

A series of detailed measurements of the lattice absorption bands of gallium arsenide has been made over the wavelength range 10–40 μ and over the temperature range 20–292°K. These results can be interpreted in terms of multiple phonon interactions involving five characteristic phonon energies. These results, along with the known elastic constants, have enabled us to supply all the relevant data for a computation of the complete phonon spectrum using an extension of the shell model.

No abstract

No abstract