Fine-structure intervals and polarizabilities of highly exciteddstates of K

Abstract

The fine-structure (fs) intervals and polarizabilities of K $n=15-20\mathrm{}$ $d$ states have been measured using a radio-frequency resonance-selective field-ionization approach. Although there is no apparent difference in the field-ionization characteristics of the $d_{\frac{3}{2}}$ and $d_{\frac{5}{2}}$ states when excited in zero electric field, we are able to observe the resonances by using a small dc electric field and time-resolved detection. The fine-structure intervals of the K $d$ states for $n\sim 20$ are inverted. Specifically, the observed fs intervals (in MHz) are: $15d$, -375.33(40); $16d$, -306.25(15); $18d$, -211.68(20); $20d$, -152.42(45). The observed tensor polarizabilities [in MHz/${\mathrm{}(\mathrm{V}/\mathrm{c}\mathrm{m})\mathrm{}}^2$] are: $15d$, -0.0208(9); $16d$, -0.0315(8); $18d$, -0.0681(18); $20d$, -0.1349(40).