We present the results of the X-ray spectral analysis of the deep survey obtained with the XMM-Newton observatory on the Lockman Hole .
The X-ray data and the cumulative source counts were reported by [ ] JB-E1 : has01 .
Our sample contains 104 sources with a count limit of 70 of which 55 have redshift identification .
The redshift distribution peaks at z \sim 0.8 , with a strong excess of low z AGN and a deficiency of sources at z > 2 compared to population synthesis models for the X-ray background .
The type 2 ( obscured ) AGN have weaker soft X-ray and optical fluxes .
They cluster around z \sim 1 .
There is a clear separation between the classical/type 1 AGN and the obscured/type 2 ones in several diagnostics involving X-ray colour , X-ray flux , optical/near IR colour and optical brightness .
Using the z subsample , we show that this separation between the AGN populations is a consequence of different absorption column densities .
The two populations have the same average spectral index , \langle \Gamma \rangle \sim 1.9 .
At the 70 count detection limit , there is also a strong overlap between the two populations in hard X-ray flux and near IR brightness .
These diagnostics should enable the classification of obscured/type 2 AGN very faint optically .