Spectral Relations between Certain Iso-electronic Systems and Sequences. Part II; Sc I, Ti II, V III, Cr IV, and Mn V

The spectra of doubly ionized vanadium, V III, triply ionized chromium, Cr IV, and quadruply ionized manganese, Mn V.—The neutral atoms of vanadium chromium, and manganese in the normal state contain five valence electrons, $3d^{3}4s^2$, six valence electrons, $3d^{5}4s$, and seven valence electrons, $3d^{5}4s^2$, respectively. The removal of two electrons, $4s^2$, from vanadium, of three electrons, $3d^{2}4s$, from chromium, and of four electrons, $3d^{2}4s^2$, from manganese yields three iso-electronic systems, V III, Cr IV and Mn V, the lowest energy levels of which arise from the three remaining electrons, $3d^3$. The spectra of these three elements so ionized resemble very closely the spectra of neutral scandium and of singly ionized titanium. Extrapolations from the already known data of Sc I, and Ti II, have led to the identification of terms arising from the electron configurations $3d^3$, $3d^{2}4s$, $3d^{2}4p$, and $3d^{2}4d$, for V III, Cr IV and Mn V.