We present a detailed characterization of the X-ray spectral properties of 761 type 1 AGN , selected from a cross-correlation of the SDSS DR5 quasar catalogue and the incremental version of the second XMM-Newton serendipitous X-ray source catalogue 2XMMi-DR2 .
The X-ray spectrum of each source is fit with models based on a simple power law to which additional cold absorption and/or soft excess features are added if an F-test at 99 % significance requires them .
The distribution of best-fitting photon indices , \Gamma , is fit with a Gaussian with mean \left < \Gamma \right > = 1.99 \pm 0.01 and dispersion \sigma _ { \left < \Gamma \right > } = 0.30 \pm 0.01 , however this does not provide a good representation of the distribution due to sources with very flat or steep \Gamma values .
A highly significant trend for decreasing \Gamma values with increasing 2-10 keV luminosity , L _ { X } , is seen but only a weak trend with redshift is found .
Intrinsic cold absorption is detected in \sim 4 \% of the sample and soft excess emission is detected in \sim 8 \% .
These values are lower limits due to the detectability being limited by the quality of the spectra and we suggest the intrinsic values may be as high as \sim 25 \% and \sim 80 \% respectively .
The levels of rest-frame absorption are higher than expected for type 1 objects ( N _ { H } = 10 ^ { 21 } -10 ^ { 23 } \textrm { cm } ^ { -2 } ) and the fraction of absorbed sources and the N _ { H } values are not seen to vary with L _ { X } or z .
The average blackbody temperature used to model the soft excesses is \left < \textrm { kT } \right > = 0.17 \pm 0.09 keV .
This temperature is found to correlate with L _ { X } but not the blackbody luminosity or the black hole mass which do correlate with each other .
A strong correlation is found between the luminosities in the blackbody and power law components suggesting that a similar fraction is re-processed from the blackbody to the power law component for the entire luminosity range of objects .
A positive correlation between \Gamma and the X-ray derived Eddington ratio is found for the sources whose mass was determined using the H \beta line , but a negative correlation is found if the CIV line is used .
No correlation is found if the MgII line is used .
No significant correlations are found between the blackbody temperature , luminosity or black hole mass with Eddington ratio , despite a link between the power law and blackbody production being indicated .
The sample includes 552 confirmed RQQ and 75 confirmed RLQ .
The RLQ are found to have higher L _ { X } values than their RQQ counterparts , suggesting an additional X-ray component , perhaps related to a jet , is present in these sources .
This component may also be the cause of the flatter \Gamma values seen in RLQ .