${4s}^2{4p}^{2}P$ intervals in the Ga isoelectronic sequence from ${\mathrm{Rb}}^{6+}$ to ${\mathrm{In}}^{18+}$

Measurements of the fine-structure splitting of the ${4s}^2{4p}^{2}P$ ground-state term of the gallium isoelectronic sequence using low-inductance sparks, laser-produced plasmas, and tokamak plasma sources are presented. The observations are in excellent agreement with semiempirical predictions using screening parametrizations, and permit a refinement of these predictions.