Non-Ritzian Nature of the 3S Terms of Mercury

AT the suggestion of Dr. A. G. Shenstone, a precise determination of the energy values of the 3 S terms as well as of the 3 D terms of mercury iodide (HgI) has been made. The light from a beam of mercury vapour diffusing from a mercury arc through a slit in the iron anode was examined by means of a Hilger E 1 instrument. This light being rich in higher series members yielded values of the 3 S terms up to 19 3 S . The plot of the quantum excess (n-n) of the terms against the term value departed considerably from a straight line relation, indicating that the terms cannot be represented by a simple Ritz formula.