  A model of a mixed helium-hydrogenic atmosphere of the isolated neutron star
1E1207.4-5209 is proposed. It is based on the assumption that the main
components in the atmosphere are the exotic molecular ions $He_2^{3+}$ and
$H_3^{2+}$ with the presence of $He^{+}, (HeH)^{2+}, H_2^{+}$ under a surface
magnetic field $\approx 4.4 \times 10^{13}$ G. In addition to two absorption
features observed by {\it Chandra} observatory (Sanwal et al, 2002) the model
predicts one more narrow absorption feature at $\approx 400$ eV.
