We present an extensive X-ray spectral analysis of the cores of 19 FRII sources in the redshift range 0.5 < z < 1.0 which were selected to be matched in isotropic radio power .
The sample consists of 10 radio galaxies and 9 quasars .
We compare our results with the expectations from a unification model that ascribes the difference between these two types of sources to the viewing angle to the line of sight , beaming and the presence of a dust and gas torus .
We find that the spectrum of all the quasars can be fitted with a single power law , and that the spectral index flattens with decreasing angle to the line of sight .
We interpret this as the effect of increasingly dominant inverse Compton X-ray emission , beamed such that the jet emission outshines other core components .
For up to 70 per cent of the radio galaxies we detect intrinsic absorption ; their core spectra are best fitted with an unabsorbed steep power law of average spectral index \Gamma = 2.1 and an absorbed power law of spectral index \Gamma = 1.6 , which is flatter than that observed for radio-quiet quasars .
We further conclude that the presence of a jet affects the spectral properties of absorbed nuclear emission in AGN .
In radio galaxies , any steep-spectrum component of nuclear X-ray emission , similar to that seen in radio-quiet quasars , must be masked by a jet or by jet-related emission .