1. Asundi and Samuel,Proc. Ind. Acad. Sci., 1936,3, 526.
2. Gaydon and Penney,Nature, 1942,150, 406.
3. Data from Sponer, except the excitation potential for A (2II) which is from Asundi,Curr. Sci., 1940,9, 503.
4. Biskamp,Zeit. f. Phys., 1933,86, 33.
5. Hagstrum and Tate,P. R., 1941,59, 354.