JANUARY 15, 1959 different degrees of thermal stability (see Table I). That a similar phenomenon can happen to Sstate atoms in a different manner is brought out by recent reports 3 on the positive and negative frequency shifts produced by various buffer gases on the hyperfine coupling constant of Cs. Photolytic experiments with hydrogen atoms in other inert matrices are in progress. 7 Q" A. Kerns, IRE Trans, on Nuclear Sci. NS-3, 114 (1956), 8 Rc Go Stoudenheimer and J 0 C 0 Moor, RCA Rev. 18, 322 (1957). 9 Gc Diemer and J 0 L 0 H, Jonker, Phillips Research Repts. £, 161 (1950). 10 A o vander Ziel, J. Appl. Phys. 28_ t 1216 (1957).