  We report results from the spectral analysis of pointed ROSAT PSPC
observations of six PG quasars and the weak-bump quasar PHL 1657. Disregarding
other frequency bands, the PSPC data are represented best by simple power-law
source spectra ($dN/dE \propto E^\Gamma$) with a slope $\Gamma = -2.5\pm 0.4$
and do not show evidence for a more complex structure. However, within the
limits given by statistics and systematical errors, a superposition of two
power-law spectra, which allows a connection to the observed UV fluxes and to
the generally flatter hard-X-ray spectra observed by EXOSAT and GINGA, is found
to be indistinguishable from a simple power-law in the PSPC energy band. For
the PG quasars, a direct connection to the observed UV flux is obtained with a
steep soft-X-ray slope $\Gamma_{sx}= -3.1\pm 0.3$, fixing the hard-X-ray slope.
For PHL 1657, the soft-X-ray spectrum seen by ROSAT is much steeper than the
GINGA spectrum, rising towards the EUV in $\nu F_\nu$, and it can not be
extrapolated down to meet the exceptionally weak UV flux. A Wien-shaped thermal
UV/soft-X-ray bump with a temperature of $\sim $50\,eV connects the UV and
soft-X-ray spectra in all cases, but gives only a poor representation of the
high signal-to-noise PSPC spectra. We discuss implications of our results for
models of the X-ray emission in quasars.

Astrophysics