  The process of radiation from high-energy electron and electron-positron pair
production by a photon in oriented single crystal is considered using the
method which permits inseparable consideration of both coherent and incoherent
mechanisms of photon emission from an electron and of pair creation by a photon
and includes the action of field of axis (or plane) as well as the multiple
scattering of radiating electron or particles of the created pair (the
Landau-Pomeranchuk-Migdal (LPM) effect). The total intensity of radiation and
total probability pair creation are calculated. The theory, where the energy
loss of projectile has to be taken into account, and found probabilities of
pair creation agree quite satisfactory with available CERN data. From obtained
results it follows that multiple scattering appears only for relatively low
energy of radiating electron or a photon, while at higher energies the field
action excludes the LPM effect.
