Information about absorption cross section

[davidpotter]

Hydrogen - Halpha cross section
i need the absorption cross section for the absorption of an H-alpha photon by a hydrogen atom, in the correct state of course, which I'm pretty sure is neutral hydrogen, n=2.
I am needing this for a project, so i also need a reliable source where this comes from.
Thanks beforehand and friendly regards,

 

[Zarqon]

I don't have the value for you, but I usually use the NIST database for atomic information. Try at http://www.nist.gov/pml/data/asd.cfm , the Lines section appears to have also transition probabilities.