Energy levels, transition frequencies and Einstein A coefficients were taken from the CDMS catalog (Müller et al 2005). Collisional rate coefficients with H2 are from Spielfiedel et al (2012), scaled by 1.36 from their rates with He. The original calculations cover energy levels up to 105 cm-1 and temperatures up to 100 K; here we provide extrapolations to 445 cm-1 and 250 K. Electron impact rates were calculated in the Born approximation by Alex Faure for temperatures from 10 to 1000 K and covering energy levels up to 945 cm-1 above ground. For a detailed description of the collision data see Nagy et al (2015).

Data with ortho and para H2 as separate collision partners were calculated by Dagdigian (2018). These data also resolve the hyperfine structure of C2H. This second datafile does not include electron collisions.

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