We have searched in the XMM-Newton public archive for quasars in the Sloan Digital Sky Survey ( SDSS ) First Data Release ( DR1 ) , and found 55 lying in the field of a XMM-Newton observation with exposure times > 20 ksec ( as of August , 2004 ) .
The 35 quasars which yielded good X-ray spectra span redshifts from 0.5 to 2.5 .
The large collecting area of XMM-Newton allows us to investigate the dependence of the X-ray spectra of quasars on luminosity , redshift and optical colors .
We find : ( 1 ) no evolution of X-ray slope ( \Gamma ) with either redshift or luminosity ; ( 2 ) no correlation between \Gamma or absorbing column density and the optical to X-ray ratio , \alpha _ { OX } ; ( 4 ) no relation between \alpha _ { OX } and optical colors .
The two latter results suggest that obscuration is not the dominant cause of the spread in X-ray slope or optical color .
We find four unusual quasars , 10 % of the sample : three are absorbed ( N _ { H } > 10 ^ { 22 } cm ^ { -2 } ) , of which one has high luminosity ( 1.5 \times 10 ^ { 44 } erg s ^ { -1 } ) ; the fourth has \Gamma =0.6 \pm 0.2 , far flatter than the typical value of 1.8-2.0 , and a strong emission line ( EW=1.2 \pm 0.4 keV ) which , if Fe-K , implies a redshift of \sim 1.4 .