  We present the analysis of multi-wavelength XMM-Newton data from the Seyfert
galaxy NGC 3783, including UV imaging, X-ray and UV lightcurves, the 0.2-10 keV
X-ray continuum, the iron K-alpha emission line, and high-resolution
spectroscopy and modelling of the soft X-ray warm absorber. The 0.2-10 keV
spectral continuum can be well reproduced by a power-law at higher energies; we
detect a prominent Fe K-alpha emission line, with both broad and narrow
components, and a weaker emission line at 6.9 keV which is probably a
combination of Fe K-beta and Fe XXVI. We interpret the significant deficit of
counts in the soft X-ray region as being due to absorption by ionised gas in
the line of sight. This is demonstrated by the large number of narrow
absorption lines in the RGS spectrum from iron, oxygen, nitrogen, carbon, neon,
argon, magnesium, silicon and sulphur. The wide range of iron states present in
the spectrum enables us to deduce the ionisation structure of the absorbing
medium. We find that our spectrum contains evidence of absorption by at least
two phases of gas: a hotter phase containing plasma with a log ionisation
parameter xi (where xi is in erg cm/s) of 2.4 and greater, and a cooler phase
with log xi centred around 0.3. The gas in both phases is outflowing at speeds
of around 800 km/s. The main spectral signature of the cold phase is the
Unresolved Transition Array (UTA) of M-shell iron, which is the deepest yet
observed; its depth requires either that the abundance of iron, in the cold
phase, is several times that of oxygen, with respect to solar abundances, or
that the absorption lines associated with this phase are highly saturated. The
cold phase is associated with ionisation states that would also absorb in the
UV.
