The Discovery of Raman Scattering in HII Regions
  We report here on the discovery of faint extended wings of H\alpha\ observed
out to an apparent velocity of ~ 7600 km/s in the Orion Nebula (M42) and in
five HII regions in the Large and the Small Magellanic Clouds. We show that,
these wings are caused by Raman scattering of both the O I and Si II resonance
lines and stellar continuum UV photons with H I followed by radiative decay to
the H I n=2 level. The broad wings also seen in H\beta\ and in H\gamma\ result
from Raman scattering of the UV continuum in the H I n=4 and n=5 levels
respectively.The Raman scattering fluorescence is correlated with the intensity
of the narrow permitted lines of O I and Si II. In the case of Si II, this is
explained by radiative pumping of the same 1023.7\AA\ resonance line involved
in the Raman scattering by the Ly\beta\ radiation field. The subsequent
radiative cascade produces enhanced Si II 5978.9, 6347.1$ and 6371.4\AA\
permitted transitions. Finally we show that in O I, radiative pumping of the
1025.76\AA\ resonance line by the Lyman series radiation field is also the
cause of the enhancement in the permitted lines of this species lying near
H\alpha\ in wavelength, but here the process is a little more complex. We argue
that all these processes are active in the zone of the HII region near the
ionisation front
