Calculation of the indirect nuclear spin-spin coupling constant of the hydrogen molecule by the truncated matrix sum method

The hydrogen molecule coupling constant has been calculated from the second-order perturbation theory summation expression of Ramsey, truncated after the first few terms. The most accurate available wave functions, those of the James-Coolidge type, give a value for the coupling constant of circa 163 hz compared with the experimental value of 278 hz. Values of the largest discrete term (the first term) calculated from various approximate wave functions vary widely. In particular, the calculation analogous to the usual molecular orbital calculation gives a value of 726 hz for the first term (compared with 199 hz calculated from James-Coolidge type wave functions).