Oxygen recombination lines from Cas A knots

Fast-moving knots (FMK) in the Galactic supernova remnant Cassiopeia A consist mainly of metals and allow us to study element production in supernovae and to investigate shock physics in great detail. We discuss and suggest observations of a previously unexplored class of spectral lines, the metal recombination lines in optical and near-infrared bands, emitted by the cold ionized and cooling plasma in fast-moving knots.