[en] Beam rocking is a new technique in nuclear microscopy which has been developed at the Oxford nuclear microprobe to produce angle-resolved channelling information from small areas of crystalline material without any rotation or translation of the sample. A beam rocking system with a focused 3 MeV proton beam has been used to detect and quantify small interface rotation angles in strained Si_1xGe_x/Si samples with 0.015< x<0.200, where the sample has been selectively etched to expose the underlying substrate. By eliminating possible rotation errors due to translation of the sample stage or backlash in the gears of a goniometer, small rotation angles have been measured, and these are found to be in good agreement with electron back scatter diffraction (EBSD) results.(authors)