Interstellar Carbodiimide (HNCNH) - A New Astronomical Detection from
  the GBT PRIMOS Survey via Maser Emission Features
  In this work, we identify carbodiimide (HNCNH), which is an isomer of the
well-known interstellar species cyanamide (NH2CN), in weak maser emission,
using data from the GBT PRIMOS survey toward Sgr B2(N). All spectral lines
observed are in emission and have energy levels in excess of 170 K, indicating
that the molecule likely resides in relatively hot gas that characterizes the
denser regions of this star forming region. The anticipated abundance of this
molecule from ice mantle experiments is ~10% of the abundance of NH2CN, which
in Sgr B2(N) corresponds to ~2 x 10^13 cm-2. Such an abundance results in
transition intensities well below the detection limit of any current
astronomical facility and, as such, HNCNH could only be detected by those
transitions which are amplified by masing.
