Millimetre-wave laboratory study of glycinamide and search for it with
  ALMA toward Sagittarius B2(N)
  Glycinamide is considered to be one of the possible precursors of the
simplest amino acid glycine. Its only rotational spectrum reported so far has
been in the cm-wave region. The aim of this work is to extend its laboratory
spectrum into the mm wave region to support its searches in the ISM.
Glycinamide was synthesised chemically and was studied with broadband
rotational spectroscopy in the 90-329 GHz region. Tunneling across a low energy
barrier between two symmetry equivalent configurations of the molecule resulted
in splitting of each vibrational state and many perturbations in associated
rotational energy levels, requiring careful coupled state fits for each
vibrational doublet. We searched for emission of glycinamide in the imaging
spectral line survey ReMoCA performed with ALMA toward Sgr B2(N). We report the
first analysis of the mm-wave rotational spectrum of glycinamide, resulting in
fitting to experimental measurement accuracy of over 1200 transition
frequencies for the ground state tunneling doublet, of many lines for tunneling
doublets for two singly excited vibrational states, and determination of
precise vibrational separation in each doublet. We did not detect emission from
glycinamide in the hot core Sgr B2(N1S). We found that glycinamide is at least
seven times less abundant than aminoacetonitrile and 1.8 times less abundant
than urea in this source. A comparison with results of astrochemical kinetics
models for species related to glycinamide suggests that its abundance may be at
least one order of magnitude below the upper limit obtained toward Sgr B2(N1S).
This means that glycinamide emission in this source likely lies well below the
spectral confusion limit in the frequency range covered by the ReMoCA survey.
Targetting sources with a lower level of spectral confusion, such as the
Galactic Center shocked region G+0.693-0.027, may be a promising avenue.
[abridged]
