The millimeter wave spectrum of methyl cyanate: a laboratory study and astronomical search in space

Aims: The recent discovery of methyl isocyanate (CH₃NCO) in Sgr B2(N) and Orion KL makes methyl cyanate (CH₃OCN) a potential molecule in the interstellar medium. The aim of this work is to fulfill the first requirement for its unequivocal identification in space, I.e. the availability of transition frequencies with high accuracy.
Methods: The room-temperature rotational spectrum of methyl cyanate was recorded in the millimeter wave domain from 130 to 350 GHz. All rotational transitions revealed A-E splitting owing to methyl internal rotation and were globally analyzed using the ERHAM program.
Results: The data set for the ground torsional state of methyl cyanate exceeds 700 transitions within J'' = 10-35 and K"_a= 0-13 and newly derived spectroscopic constants reproduce the spectrum close to the experimental uncertainty. Spectral features of methyl cyanate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methyl cyanate are provided.

This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00009.SV. Tables 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A75