Abstract: There is disclosed a time-of-flight ion-scattering spectrometer which comprises an ultra-high vacuum chamber sized to accommodate a flight path of sufficient length to provide unit mass resolution at all detection positions and which has means for detecting both ions and neutral particles at both continuously variable forward scattering and backscattering angles. Spectra of both neutrals plus ions as well as neutrals only can be obtained in the same experiment. The polar incidence angle, surface azimuthal angle, and scattering (or recoil) angle can all be varied continuously and independently of one another. The associated method, Scattering and Recoiling for Electron Distributions and Structure (SREDS), allows one to determine atomic structure of substrate surfaces, the structure of adsorbate sites, and electron distributions above surfaces. Even light adsorbates such as hydrogen, carbon, and oxygen can be quantitated by this method.