“…It is easily shown that (1/µ 79,81 − 1/µ 81 ) = (1/µ 79 − 1/µ 79,81 This anomalous isotope dependence in the electronic term values has an important consequence for the models currently used to fit several isotopomers simultaneously (5,7,11). The expression used to fit the Dunham coefficients of several isotopomers is usually written as are isotopically independent parameters.…”