We present experimental observations of planar and axial channeling ra
diation emitted by relativistic electrons and positrons traversing a B
eO crystal. Values of thermal vibration amplitudes are obtained, and f
ound to be in agreement with those obtained by other methods, namely,
x-ray and neutron diffraction. The standard channeling-radiation theor
y matches correctly the observed radiation spectra when the particle i
s channeled along principal planes. Some of the planes with higher Mil
ler indices give radiation spectra that can only be explained by the c
oupling of the particle wave function to neighboring axes or planes, o
r by population redistribution within the band.