Energy levels, transition frequencies and Einstein A coefficients were taken from CDMS version 4 of May 2007. Collisional rate coefficients are from Dumouchel et al (2010) who have also made calculations for HNC. The set of rate coefficients was scaled by a factor 1.37 to represent collisions with H2. Electron collision rates are taken from Faure et al (2007) and cover the levels up to J=8 for temperatures from 5 to 800 K.
We also provide older collisional calculations from Green & Thaddeus (1974) and Green (unpublished data), extrapolated for the temperature range from 5 to 1200 K, and including energy levels up to J=29. for collisions with He. This dataset may still be useful to model high-J line observations of HCN. For details on the extrapolation see Schöier et al. (2005).
A third datafile where the hyperfine splitting (hfs) of the J=1 level is taken into account is also presented. In this file, the transition frequencies for the J=2-1 transition have been calculated with all the hyperfine levels in the J=2 collapsed into a single level.