About this website
Photodissociation and photoionization are major destruction processes of molecules in any astrophysical region where ultraviolet photons penetrate, including diffuse and translucent clouds, dense PDRs, the surface layers of protoplanetary disks, and cometary and exoplanetary atmospheres.
This website provides the basic molecular data needed to compute photodestruction rates in various environments, with references to the original sources of the cross section data. Only species for which laboratory or theoretical data are available have been included. Overview papers papers describing the methods, cross section data and an assessment of the accuracy of the photorates are provided.
What can I find here?
- Atomic and molecular photoabsorption, photodissociation, and photoionisation cross sections in numerical form.
- Figures displaying the cross sections.
- Photo rates for various stellar radiation fields and for cosmic-ray induced radiation.
- Depth-dependent shielding functions
- Additional detailed data on N2 and CO isotopologues.
- Data on the photodissociation fragment branching ratios of H2O and NH3.
- Data on the photodesorption of H2O from interstellar ices.
- References for the sources of data and some overview paper describing the website contents.
When using material from this site, please cite one of the overview papers. In cases of specific molecules, please cite the original source of the cross sections as appropriate.
- 1 March, 2017:
- In some cases due to experimental noise there are small negative values for cross sections. These have been adjusted to zero to avoid any possible numerical problems.
- The S photoionisation cross section included a small value at longer wavelength than its threshold, due to a finite experimental resolution. This has been set to zero. This reduces its small photodissociation rate by Ly-alpha radiation to zero.
- Added a third cross section file format. These contain that same data as the binary hdf5 files but in a text file for easy usage. Lines and continuum are included in a single cross section. File sizes and load times are likely larger and longer for this data relative to the hdf5 formatted data.
- January, 2017: Updated database in view of new data in Heays et al. 2017.