  We present high resolution (0."4) observations of HNC J=3-2 with the
SubMillimeter Array (SMA). We find luminous HNC 3-2 line emission in the
western part of Arp220, centered on the western nucleus, while the eastern side
of the merger shows relatively faint emission. A bright (36 K), narrow (60
km/s) emission feature emerges from the western nucleus, superposed on a
broader spectral component. A possible explanation is weak maser emission
through line-of-sight amplification of the background continuum source. There
is also a more extended HNC 3-2 emission feature north and south of the
nucleus. This feature resembles the bipolar OH maser morphology around the
western nucleus. Substantial HNC abundances are required to explain the bright
line emission from this warm environment. We discuss this briefly in the
context of an X-ray chemistry and radiative excitation. We conclude that the
luminous and possibly amplified HNC emission of the western nucleus of the
Arp220 merger reflects the unusual, and perhaps transient, environment of the
starburst/AGN activity there. The faint HNC line emission towards Arp220-east
reveals a real difference in physical conditions between the two merger nuclei.
