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Computed photoabsorption cross sections of ¹⁴N₂, ¹⁴N¹⁵N, and ¹⁵N₂, over a range of temperatures from 0 K to 300K, are available for download. The cross sections are presented in 0.01 cm^-1 increments over the 100,000 to 105,000 cm^-1 region. Background spectroscopic information and a description of the coupled-channel Schrödinger equation model underlying the computations are summarized in Spectroscopic Information.

Please note that the coupled-channel model is under continuous development and extension; questions regarding the specifics of the datasets being made available for download should be directed to the authors.

For a given temperature, the total cross section is evaluated from individual coupled-channel rotational-transition cross sections, each computed over the full energy range and then added together, weighted by appropriate Boltzmann factors. The cross section spectrum is then convolved with a Gaussian function associated with the corresponding gas temperature. The natural (Lorentzian) widths of lines in this model reflect predissociation rates only; radiative decay rates are not explicitly reflected in the model output. This has a negligible effect on the final temperature-dependent cross section, even for the few bands for which radiative rates are comparable to predissociation rates (in those cases, the Lorentzian line widths are much smaller than the Doppler width, and the line shapes are essentially Gaussian).

Photochemical calculations often require photodissociation cross sections as well as photoabsorption cross sections. As described in Liang et al. (2007), photodissociation cross sections can be derived by correcting the modeled photoabsorption cross sections using coupled-channel-computed predissociation quantum yields, determined on a rotational basis by comparison between the relevant predissociation and radiative line widths. Since almost all absorption by N₂ results in dissociation in the 100,000 to 105,000 cm^-1 region, in practice corrections are necessary only for the b(1) – X(0) and c′₄(0) – X(0) bands.

Cross section files for each isotopologue are available at fifteen temperatures. Each file, in ASCII format, is approximately 10 Mbytes in size. Accompanying pdf files display logarithmic plots of the cross sections. Individual bands are identified in Spectroscopic Information. If other temperatures in the 0 to 300 K range are needed, please contact the authors.

Photoabsorption Cross Sections Files
Click on the icon to open the dat files and on the icon to open the pdf files.

0K

5K

10K

20K

40K

80K

120K

160K

180K

200K

220K

240K

260K

280K

300K

14N2

14N15N

15N2

When using this data, please cite, (a), the relevant peer-reviewed journal articles describing the development and the specifics of the coupled-channel model (see References) and, (b), Lewis, B. R, Heays, A. N., Gibson, S. T., & Stark, G., N₂ photoabsorption cross sections in the vacuum ultraviolet, /Physics/gstark/N2_ANU_cross_sections, Wellesley College, Wellesley, MA. .

We will be happy to notify users of updates or corrections; please email the authors for such notifications.