Spectra of the z _ { em } = 3.268 quasar PKS 2126–158 have been obtained in the range \lambda \lambda 4300 - 6620 Å with a resolution R \simeq 27000 and an average signal-to-noise ratio s / n \simeq 25 per resolution element .
The list of the identified absorption lines is given together with their fitted column densities and Doppler widths .
The modal value of the Doppler parameter distribution for the Ly \alpha lines is \simeq 25 km s ^ { -1 } .
The column density distribution can be described by a power-law dn / dN \propto N ^ { - \beta } with \beta \simeq 1.5 .

12 metal systems have been identified , two of which were previously unknown .
In order to make the column densities of the intervening systems compatible with realistic assumptions about the cloud sizes and the silicon to carbon overabundance , it is necessary to assume a jump beyond the He II edge in the spectrum of the UV ionizing background at z \sim 3 a factor 10 larger than the standard predictions for the integrated quasar contribution .

An enlarged sample of C IV absorptions ( 71 doublets ) has been used to analyze the statistical properties of this class of absorbers strictly related to galaxies .
The column density distribution is well described by a single power-law , with \beta = 1.64 and the Doppler parameter distribution shows a modal value b _ { CIV } \simeq 14 km s ^ { -1 } .
The two point correlation function has been computed in the velocity space for the individual components of C IV features .
A significant signal is obtained for scales smaller than 200 - 300 km s ^ { -1 } , \xi ( 30 < \Delta v < 90 { km s } ^ { -1 } ) = 32.71 \pm 2.89 .
A trend of decreasing clustering amplitude with decreasing column density is apparent , analogously to what has been observed for Ly \alpha lines .