  The $d^5$ electron configurations under the crystal field, spin-orbit
coupling, and Coulomb interaction give rise to a plethora of profound ground
states. Ruthenium perovskite oxides exhibit a number of unconventional
properties yet the Ru$^{4+}$ state ($4d^4$) is usually stable in these
materials. In this regard, Ru$^{3+}$ ions in perovskite materials are expected
to be a mesmerising playground of $4d^5$ electron configurations. Here, we
report measurements of x-ray photoemission spectroscopy on recently synthesized
perovskite ruthenium oxide thin films, LaRuO$_3$ and NdRuO$_3$, whose valence
state of the ruthenium ions is trivalent. We discuss correlation and spin-orbit
effects from the valence-band spectra, in particular an additional peak
structure around 3-5 eV, reminiscent of the so-called 3 eV peak observed in
Sr$_2$RuO$_4$. Moreover, we find that the core-level spectra of these materials
are quantitatively different from those in other ruthenates which possess
Ru$^{4+}$ ions, e.g., SrRuO$_3$. We therefore argue that the core level spectra
of LaRuO$_3$ and NdRuO$_3$ are peculiar to the Ru$^{3+}$ states.
