Metastable hydrogen molecules. IV. Vibrational analysis and spin–rotation interaction

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Abstract
This paper presents new experimental data which improves by an order of magnitude the precision of our understanding of the fine structure of the hydrogen molecule. By means of the molecular beam,magnetic resonance method, we find that the v=0, 1, and 2 vibrational levels of parahydrogen in the c 3Π u state are metastable. Measurements of four fs intervals in the N=2 rotational level of these three vibrational levels complete the set of six such measurements. In addition, we report eleven more intervals in the N=1 rotational level of the v=1 vibrational state, to comple the 13 possible measurements in that state. The four fine structure constants, including the spin‐rotation constant C, are determined for all the v=0 and v=1, N=1, and N=2 levels. The linear combinations of constants, A+5C and B 0+√6 B 2, are found for N=2, v=2 also. Completion of vibrational assignments and inclusion of spin‐rotation interaction now makes experimentally determined constants interpretable to a fraction of a percent in most cases. A method is given for using spectroscopic constants to find the vibrational average of an operator.