  The energy and photoluminescence spectra of a two-dimensional electron gas in
the fractional quantum Hall regime are studied. The single-particle properties
of reversed-spin quasielectrons (QE$_{\rm R}$'s) as well as the
pseudopotentials of their interaction with one another and with Laughlin
quasielectrons (QE's) and quasiholes (QH's) are calculated. Based on the
short-range character of the QE$_{\rm R}$--QE$_{\rm R}$ and QE$_{\rm R}$--QE
repulsion, the partially unpolarized incompressible states at the filling
factors $\nu={4\over11}$ and ${5\over13}$ are postulated within Haldane's
hierarchy scheme. To describe photoluminescence, the family of bound
$h($QE$_{\rm R})_n$ states of a valence hole $h$ and $n$ QE$_{\rm R}$'s are
predicted in analogy to the found earlier fractionally charged excitons
$h$QE$_n$. The binding energy and optical selection rules for both families are
compared. The $h$QE$_{\rm R}$ is found radiative in contrast to the dark $h$QE,
and the $h($QE$_{\rm R})_2$ is found non-radiative in contrast to the bright
$h$QE$_2$.
