We experimentally investigate Bragg reflection of atoms from a standing lig
ht wave. We focus on the influence of small angular deviations from the exa
ct Bragg resonance onto the reflection probability. The Bragg resonance has
a finite acceptance angle, which depends on the light intensity. Within th
is acceptance angle, an oscillatory behavior of the reflection probability
as a function of the angle is observed. [S1050-2947(99)02302-1].