Channeling of antiprotons

We present experimental results for channeling of 1.4 MeV antiprotons in a 0.5 pm thick (100) silicon crystal. The 'half-widths' for the observed channeling effect, Deltapsi(p)(_), is significantly smaller than the Lindhard angle psi(1), as is the case for electrons where typical angles are about Deltapsi(e-) similar or equal to 0.6psi(1). In the case of protons and positrons, critical angles are of the order Deltapsi(e+) similar or equal to Deltapsi(p) similar or equal to psi(1). Thus, we may attribute the difference between Deltapsi(p)(.e-)(_) and Deltapsi(p.e+) to the sign of charge of the penetrating particle. (C) 2003 Elsevier Science B.V. All rights reserved.