Polarizability of Kr{sup 6+} from high-L Kr{sup 5+} fine-structure measurements

The transition between n=55 and n=109 Rydberg levels of Kr{sup 5+} has been studied at high resolution using the resonant excitation stark ionization spectroscopy method. Resolved excitation of L=6, 7, 8, and 9 levels in n=55 lead to a determination of the fine-structure energies of these levels. Interpreted with the long-range polarization model, this leads to a measurement of the dipole polarizabilities of Zn-like Kr{sup 6+}, {alpha}{sub d}=2.69(4)a{sub 0}{sup 3}. Obtaining a value of the quadrupole polarizability from the data will require additional theoretical input. Factors contributing to the signal and noise levels in measurements of this type are discussed.