We present experimental observations of planar and axial channeling radiation emitted by relativistic electrons and positrons traversing a BeO crystal. Values of thermal vibration amplitudes are obtained, and found to be in agreement with those obtained by other methods, namely, x-ray and neutron diffraction. The standard channeling-radiation theory matches correctly the observed radiation spectra when the particle is channeled along principal planes. Some of the planes with higher Miller indices give radiation spectra that can only be explained by the coupling of the particle wave function to neighboring axes or planes, or by population redistribution within the band.

• Received 16 February 1993

DOI:https://doi.org/10.1103/PhysRevB.48.5818