Presented is the first experimental demonstration of a dramatic radiative redistribution in transverse states for multi-GeV electrons/positrons, interacting with strong crystalline fields. Detailed analysis of energy loss, photon multiplicities, and scattering distributions leads to new physical insight into open questions such as radiative cooling/heating of the beams in aligned crystals, validity of the constant-field approximation, radiative capture of random particles (“feed in”) into channeled states, and the Landau-Pomeranchuk effect in multiphoton radiation spectra.

• Received 19 February 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.3415