Atomic Diamagnetism and Diamagnetically Induced Configuration Mixing in Laser-Excited Barium

The diamagnetic Zeeman effect has been isolated by observing energy shifts of the $6s6p{}_{}{}^1{}_{}{}^{}{P}_1_{}^{\circ }{}_{}{}^{}-6\mathrm{sns}$ ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ Rydberg series in laser-excited Ba in magnetic fields of 20-40 kG. Perturbation of this series by the $5d7d{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ level reduces the shift below the hydrogenic value for $n=18\mathrm{}$. Magnetically induced mixing between the $6sns{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and $6snd{}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ series causes both an enhancement in intensity of the higher members of the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ series and deviations of the shifts from the hydrogenic values.