  The description of the narrowing effect at high pressures is demonstrated on
the example of CO2-He absorption for Q-, P-, and R-branches and for the head of
the R-branch. The problem is focused on the physical meaning of this phenomenon
that should be associated with the angular and translation momentum transfer to
matter from the photon absorbed. The effect is described in the approximation
of the single line without the conventional line mixing. A narrowing function
is introduced that links the absorption in the resonance region with the one in
far wings. This function enlarges the absorption of a single line approximately
in two times in the resonance region at high pressures and decreases the one
approximately in 20 times in far wings in comparison with the Lorentzian,
independently of the type of molecule and pressures. The halfwidth of a single
line is assumed to have a nonlinear pressure dependence and approaches to a
saturated value at high pressures.
