C₂ Swan Bands

This shows an example of an electronic spectrum. The constants are taken from G. M. Lloyd and P. Ewart, J Chem. Phys. 110, 385 (1999). The line positions agree with the calculated line positions from the paper to about 0.0001 cm^-1. A small adjustment was required to the constants - the difference between p_D+2q_D between the two states is taken to be -9.42 rather than -0.942 as given in Table II. (The value given in Table II is not the value quoted by Prasad and Bernath as quoted in the footnotes to the table.) Note that LimitSearch="True" is required for the F1/F2/F3 quantum numbers to be calculated correctly. See below for a larger example involving several vibrational states.

This is a more complicated example, including many vibrational bands. Note that all the vibrational states of a given electronic are all in the same manifold, though this is not essential. The constants are taken from A. Tanabashi, T. Hirao, T. Amano and P. F. Bernath, Astrophys. J. SuppSer.169, 472 (2007), with the transition moments calculated from the Einstein A coefficients given in J. S. A. Brooke, P. F. Bernath, T. W. Schmidt, and G. B. Bacskay, J Quant. Spect. Rad. Trans, 124, 11 (2013). The calculated line positions agree with the line positions given by Tanabashi et al for clear, unperturbed lines with an average error of 0.03 cm^-1. There are some known local perturbations which are not included in this model. Note that this was updated in Feb 2017; the previous version had several estimated constants.

This data file is set up for absorption, though the Swan bands are most commonly seen in emission. To transform to an emission spectrum set Initial to true for the d state and false for the a state, and follow the other instructions under Emission Spectra.