The diffusion equation of cosmic-ray nucleons is exactly integrated using
the successive approximation method for a general distribution of the
primary component, and taking into account the rising nucleon-air
cross sections with energy. The interaction probability law for the
nucleon in the atmosphere is obtained as a consequence of the respective
diffusion equation. If the nucleon-air cross sections rise logarithmically,
this probability law assumes a binomial form, and for the constant cross
section, it is purely Poissonian. The well known approximate solution is
compared with our exact solution. It is found that the former always gives
a nucleon number greater than ours by, for example, 15-25% in the
energy region 30-10 000 GeV at sea level in the case of the mean
inelasticity ⟨κ⟩ = 0.60. It is also shown that a fairly
accurate description of nucleon flux at sea level (1030 g cm-2) and hadron intensities at 840 g cm-2 and at
1030 g cm-2 are obtained with ⟨κ⟩
varying between 0.55 and 0.60.