  The possible sources of one-photon radiation as background for quasi-elastic
reaction nu_mu+n to mu^-+p are considered. The ones are relevant in experiments
on determination of oscillation parameters at low neutrino energies (E_nu^lab~1
GeV). The estimation for the cross section of reaction nu_mu+n to mu^-+p+gamma
is given at E_nu^lab=0.7 GeV as 0.65% from the corresponding cross section of
quasi-elastic reaction.
