The diffuse molecular component in the nuclear bulge of the Milky Way
  Context: The bulk of the Molecular gas in the Central Molecular Zone (CMZ) of
the Galactic center region shows warm kinetic temperatures, ranging from $>20$
K in the coldest and densest regions (n$\sim 10^{4-5}$ cm$^{-3}$) up to more
than 100 K for densities of about n$\sim 10^3$ cm$^{-3}$. Recently, a more
diffuse, hotter ($n \sim 100$ cm$^{-3}$, $T\sim 250$ K) gas component was
discovered through absorption observations of H$_3^+$. This component may be
widespread in the Galactic center, and low density gas detectable in absorption
may be present even outside the CMZ along sightlines crossing the extended
bulge of the Galaxy. Aims: We aim to observe and characterize diffuse and low
density gas using observations of 3-mm molecular transitions seen in
absorption. Methods: Using the Atacama Large (sub)Millimeter Array (ALMA) we
observed the absorption against the quasar J1744-312, which is located towards
the Galactic bulge region at $(l,b)=(-2{^\circ}.13,-1{^\circ}.0)$, but outside
the main molecular complexes. Results: ALMA observations in absorption against
the J1744-312 quasar reveal a rich and complex chemistry in low density
molecular and presumably diffuse clouds. We detected three velocity components,
at $\sim $ 0, $-153$, and $-192$ km s$^{-1}$. The component at $\sim 0$ km
s$^{-1}$ could represent gas in the Galactic disk while the velocity components
at $-153$, and $-192$ km s$^{-1}$ likely originate from the Galactic bulge. We
detected 12 molecules in the survey, but only 7 in the Galactic bulge gas.
