  Within the framework of a flat cosmological model a propagation of an
instantaneous burst of isotropic radiation is considered from the moment of its
beginning at some initial redshift z0 to the moment of its registration now (at
z=0). We take into account Thomson scattering by free electrons and scattering
in La and Lb lines of primordial hydrogen and in lines 1s2 - 1s2p, 1s3p
(1S-1P*) of HeI. It is shown that relative amplitude of spectrum distortions
caused by scattering in these lines may be from 1000 to 10000 times greater
than maximum possible amplitude due to scattering in subordinate lines
considered in our previous paper (Dubrovich, Grachev, 2015). In a linear
approximation on the optical thickness in the lines the profiles of distortions
in resonance lines turn out to be purely in absorption and do not depend on
both direction and distance to the burst center in contradistinction to the
profiles in subordinate lines. The profiles contain jumps on frequencies
corresponding to appearance of a source (burst) at a given redshift z=z0. For
z0=5000 the jumps in hydrogen La and Lb lines are on frequencies 493 and 584
GHz respectively and jumps in two HeI lines are on 855 and 930 GHz for z0=6000.
Relative magnitude of jumps amounts to 1e-4 - 3e-3.
