  We present high-resolution X-ray spectra of cloud-shock interaction regions
in the eastern and northern rims of the Galactic supernova remnant Puppis A,
using the Reflection Grating Spectrometer onboard the XMM-Newton satellite. A
number of emission lines including K alpha triplets of He-like N, O, and Ne are
clearly resolved for the first time. Intensity ratios of forbidden to resonance
lines in the triplets are found to be higher than predictions by thermal
emission models having plausible plasma parameters. The anomalous line ratios
cannot be reproduced by effects of resonance scattering, recombination, or
inner-shell ionization processes, but could be explained by charge-exchange
emission that should arise at interfaces between the cold/warm clouds and the
hot plasma. Our observations thus provide observational support for
charge-exchange X-ray emission in supernova remnants.
