Theory of crystal-assisted radiation and pair creation for imperfect alignment

Calculations of the angular dependence of the crystal-assisted pair creation rate and radiation intensity have been carried out using a semi-classical formalism which is valid for very high energies. The results show that crystal-assisted processes occur with nearly undiminished intensity at incident angles considerably larger than the classical chanelling angles. Pair creation is suppresed less by an increasing angle than is radiation, and in some cases the pair creation rate increases with the angle before it diminishes.