  We have developed in detail the theory of X-ray line and continuum production
due to atomic interactions of accelerated ions, incorporating in our
calculations information from a broad range of laboratory measurements. We
applied our calculations to the Orion region from which nuclear gamma-ray lines
were observed with the COMPTEL instrument on CGRO. The accelerated particles
which produce this gamma-ray emission via nuclear reactions also produce X-ray
lines via atomic interactions. We predict strong line emission in the range
from 0.5 to 1 keV, mainly due to de-excitations in fast O ions. While much of
the diffuse X-ray emission observed with ROSAT from Orion could be due to
accelerated ions, the current X-ray data do not provide unambiguous signatures
for such an origin. If future observations with high spectral resolution would
confirm the predicted X-rays, the combined analysis of the X-ray and gamma-ray
data will set important constraints on the origin of the accelerated particles
and their interaction model.
