  The effect of isotope shifts of nuclear magnetic resonance (NMR) frequency in
xenon isotopes 129Xe and 131Xe polarized by optically-oriented alkali metal
atoms is not only of fundamental interest, but also of practical significance
since it is the main factor limiting the accuracy of a whole class of
prospective navigation and metrological devices. We have studied the parametric
dependences of the isotope shift and have shown that this effect is largely due
to incomplete averaging of a inhomogeneous local magnetic field by two xenon
isotopes. A numerical model has been derived, which qualitatively describes the
effect of isotope frequency shift and provides a good quantitative agreement
with the experiment.
