  This poster presents single-dish and aperture-synthesis observations of the
J=1-0 (lambda~3 mm) transitions of HCO+, HCN, and N2H+ towards the Serpens
star-forming region. Jets driven by young stars affect the structure and the
chemistry of their surrounding cloud, and this work aims to assess the extent
to which the emission of these three molecular lines is dominated by such
processes. In Serpens I find that N2H+ 1-0 traces the total amount of material,
except in two regions slightly ahead of shocks. In contrast, the HCO+ and,
especially, HCN emission is dominated by regions impacted by outflows. One
previously unknown, strongly shocked region is located ~0.1 pc northwest of the
young stellar object SMM 4. There is a marked spatial offset between the peaks
in the HCN and the N2H+ emission associated with shocked regions. I construct a
simple, qualitative chemical model where the N2H+ emission increases in the
magnetic precursor of a C-type shock, while N2H+ is destroyed deeper in the
shock as the neutrals heat up and species like HCN and water are released from
icy grain mantles. I conclude that N2H+ is a reliable tracer of cloud material,
and that unresolved observations of HCO+ and HCN will be dominated by material
impacted by outflows.
