Sulfur dioxide
LAMDA | RADEX on-line

Energy levels, transition frequencies and Einstein A coefficients were taken from JPL. The collisional rates are taken from Green (1995) and were calculated for temperatures in the range from 25 to 125 K including energy levels up to 62 cm-1 for collisions with He. This set of collisional rate coefficients, multiplied by 1.4 to represent collisions with H2, was extrapolated to include energy levels up to 250 cm-1 and for a range of temperatures from 10 to 375 K. For details on the extrapolation see Schöier al. (2005).

Collision rates of SO2 with H2 have been calculated by Cernicharo et al (2011), but only for temperatures up to 30 K. While the direct use of these rates is limited to cold interstellar clouds, the calculation shows that collisions with H2 are about 3 times more effective in exciting SO2 than He, even after scaling for the reduced mass, because the long-range interaction is significant.

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