Deepest Terms in Ions of the Isoelectronic Sequence A I-Mn VIII

Radiations corresponding to the energy differences between the terms 3p⁶¹S₀-3p⁵4s³P₁⁰,¹P₁⁰ in Ti V, V VI, Cr VII, Mn VIII and 3p⁶¹S₀-3p⁵5s³P₁⁰,¹P₁⁰ in V VI and Cr VII have been observed. These radiations connect the upper states with the deepest terms in each ion and therefore enable the calculation of the ionization potentials. The identification of the lines was facilitated by the use of constant second difference displaced frequency diagrams. The limits of the 3p⁶¹S₀-3p⁵ ms ³P₁⁰,¹P₁⁰ series have been calculated for V VI and Cr VII, and have an estimated error in the value of the deepest terms of 0.5 percent. The values of the deepest terms of V VI and Cr VII, calculated from series limits, make possible the calculation of the absolute value of the deepest terms of Sc IV, Ti V and Mn VIII from a Moseley diagram.