  Selectively excited photoluminescence (SPL) of an array of self-organized
In$_{0.5}$Ga$_{0.5}$As quantum dots has been measured in a magnetic field up to
11T. Anomalous magnetic field sensitivity of the SPL spectra has been observed
under conditions for which the regular photoluminescence spectra is insensitive
to the magnetic field due to large inhomogeneous broadening. The anomalous
sensitivity is interpreted in terms of the repulsion of excited levels of the
dots in a random potential. A theory presented to describe this phenomena is in
excellent agreement with the experimental data. The data estimated the
correlation in the positions of excited levels of the dots to be 94%. The
magnetic field dependence allows the determination of the reduced cyclotron
effective mass in a dot. For our sample we have obtained
$m_em_h/(m_e+m_h)=0.034m_0$.
