Abstract
The cross section for the formation of H(n=2) or D(n=2) by photodissociation for the three isotopes H2, HD, and D2 has been measured using synchrotron radiation between 500 and 200 Å. The comparison with computed cross section curves shows the importance of the Q11Πu Q21Πu(1) neutral states of the 2pπ2Πu ionization continuum. Contribution from Rydberg states converging to the 2pπ2Πu state of H+2 is suggested. No isotopic effect can be confirmed.