Detection of hydrogen atoms via the 3s and 3d states

The wavelength 205.14 nm is absorbed by many hydrogen containing molecules which then dissociate to from hydrogen atoms. These in turn can absorb two more 205.14 nm photons and reach the 3s of the 3d state. They can absorb a third photon and form hydrogen ions or decay to the ground state by stepwise fluorescence, first emitting the Balmer a line at 656.2 nm (3s or 3d → 2p) and then the layman a line at 121.6 nm (2p → 1s). Thus the hydrogen atom kinetic energy can be probe in three different ways. This method broadens greatly the possibilities of investigating photodissociations leading hydrogen atom products. Results are given for HS, HBr, HI, and CH3NH2.