  We report on the observation of OVII Doppler line broadening in a compact
knot at the edge of SN 1006 detected with the Reflective Grating Spectrometer
on board XMM-Newton. The observed line width of sigma = 3.4+/-0.5 eV at a line
energy of 574 eV indicates an oxygen temperature of kT = 528+/-150 keV.
Combined with the observed electron temperature of 1.5 keV the observed
broadening is direct evidence for temperature non-equilibration in high Mach
number shocks, and slow subsequent equilibration. The OVII line emission allows
an accurate determination of the ionization state of the plasma, which is
characterized by a relatively high forbidden line contribution, indicating
log(n_e t) ~ 9.2.
