CO
Carbon monoxide
LAMDA | RADEX on-line

After H2, CO is the most abundant molecule in the ISM. As CO is commonly used to trace the mass content of circumstellar and interstellar matter it is of great importance to have accurately determined properties for this molecule.

Energy levels, transition frequencies and Einstein A coefficients were taken from CDMS and JPL (However, see notes in the case of 13CO). The collisional rate coefficients are adopted from Yang et al. (2010) and includes energy levels up to J=40 for temperatures ranging from 2K to 3000K. These new rate coefficients, for collisions with both para- and ortho-H2, use close-coupling and coupled-states approximation scattering calculations and the interaction potential of Jankowski and Szalewicz (2005).

The new set of collisional rate coefficients calculated by Yang et al. superseeds previous extrapolation efforts and should be used for modelling. For the time the old (now obsolete) CO data file with collisional rate coefficients from Flower (2001) and Wernli et al. (2006) is still available. These rates were calculated for temperatures in the range from 5 to 400 K including energy levels up to J=29 and J=20 for collisions with para-H2 and ortho-H2, respectively. The datafile containes extrapolation to include energy levels up to J=40 and collisional temperatures up to 2000 K. For details on the extrapolation see Schöier et al. (2005).

Extrapolation to even higher J-levels (J=80) was performed by David Neufeld in December 2010 and also provided here. A publication about this extrapolation is in preparation.

  • References
    Flower, D.R. 2001, J. Phys. B, 34, 2731
    Jankowski P., Szalewicz K. 2005, JChPh 123, 10, 104301
    Schöier, F.L, van der Tak, F.F.S., van Dishoeck, E.F., Black, J.H. 2005, A&A 432, 369
    Wernli M., Valiron P., Faure A., Wiesenfeld P., Jankowski P., Szalewicz K. 2006, A&A 446, 367
    Yang, B., Stancil, P.C., Balakrishnan, N.; Forrey, R. C. 2010, ApJ 718, 1062

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