  Effects associated with the change in the local density of photonic states in
a periodic structure based on alternating \textit{a}-Si$_{1-x}$C$_x$:H and
\textit{a}-SiO$_2$ amorphous layers forming a one-dimensional (1D) photonic
crystal have been analyzed. The use of \textit{a}-Si$_{1-x}$C$_x$:H as the
emitting material made it possible to examine the transformation of the
photoluminescence spectrum contour that is comparable in width with the
photonic stop-band. It was experimentally demonstrated that the emission is
enhanced and suppressed in the vicinity of the stop-band. The relative
intensities of the luminescence peaks at different edges of the stop-band vary
with the detuning of the stop-band position and photoluminescence peak of a
single \textit{a}-Si$_{1-x}$C$_x$:H film. The Purcell effect in the system
under consideration was theoretically described by the method in which the
local density of photonic states is calculated in terms of a 1D model. %A good
agreement was obtained between the experimentally measured and calculated
spectra. It was shown that the specific part of local density of states
substantially increases at the long-wavelength (low-frequency) edge of the
stop-band of a 1D photonic crystal as a result of the predominant localization
of the electric field of the light wave in the spatial regions of
\textit{a}-Si$_{1-x}$C$_x$:H which have a higher relative permittivity as
compared with \textit{a}-SiO$_2$.
