Effect of coherent energy width in proton capture by /sup 12/C

Spectra of ..gamma.. rays from the reaction /sup 12/C( p,..gamma..)/sup 13/N have been studied in a thick target in the proton-energy range 1500--2000 keV. The experimental results indicate the existence of an anomaly in the radiative capture of protons with energy about 1700 keV in a thick carbon target, which appears in the fact that for identical proton energies the cross section for capture by /sup 12/C in a thick target differs from the cross section for the same reaction measured in a thin target. It has been possible to describe the observed effect on the assumption that in the slowing down of protons with energy approx.1.7 MeV in a thick carbon target a wave packet with a width of the order of 40 keV is formed.