The Structure of the Ultra-Violet Spectrum of the Hydrogen Molecule

The absorption spectrum of the hydrogen molecule has been photographed and also the emission spectrum under various discharge conditions. In the region between 1000A and 1650A the bands belong chiefly to two systems with a common final electronic state, which is the lowest state of the molecule. The correctness of the classification is proved by combination relations and the variation of the rotational energy with the vibrational quantum number. The Lyman bands are emitted when, by collisions of the second kind with excited metastable argon atoms, the hydrogen molecule is brought into the first excited electronic state with three vibrational quanta. From the energy diagram which is obtained from the analysis of the spectrum it follows that the resonance potential of the hydrogen molecule is 11.1 volts. The heat of dissociation of the hydrogen molecule is found by two independent methods to be 4.34 and 4.38 volts, respectively.