  The Owens Valley Radio Observatory (OVRO) millimeter array was used to make
observations of the CS(2-1) line (at 97.981 GHz) arising from the G0.07+0.04
region of the ``-30 km/s'' molecular cloud near the Galactic center with a
spatial resolution of ~8". The ionized edges of this cloud forms the Arched
Filament HII regions which are ionized by the adjacent Arches stellar cluster.
The OVRO data were combined with single-dish data obtained at the 30-m IRAM
telescope by Serabyn & Guesten (1987). A comparison of this CS(2-1) data and
the H92alpha recombination line data of Lang, Goss & Morris (2001) reveals that
the ionized and molecular gas are physically related, but that their velocities
in this region differ by up to 35 km/s. This difference in velocity can be
understood if the gas that gave rise to the G0.07+0.04 HII region has been
fully ionized. An overall comparison of the molecular and ionized gas across
the entire -30 km/s cloud based on the single dish CS(2-1) data and the
H92alpha line data illustrates that such differences in velocity between the
ionized and molecular gas are common and that the geometrical arrangement of
these components is complicated. Much of the ionized gas resides on the near
side (to the observer) of the molecular cloud; however, in several regions,
some molecular material must lie in front of the HII region. The Arches stellar
cluster therefore appears to be located in the midst of the molecular clouds
such that some of the near-side cloud surfaces along our line of sight have not
been exposed to the ionizing radiation.
