Knight Shift in Potassium

The ${\mathrm{K}}^{39}$ nuclear magnetic resonance has been observed in metallic potassium and in aqueous solutions of KN${\mathrm{O}}_3$ and ${\mathrm{K}}_3$Co${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_6$. From these observations a Knight shift of (0.248±0.005)% has been obtained. Using Pines' value 0.60×${10}^{-6\mathrm{}}$ for the spin susceptibility gives $P_f=0.95\mathrm{} {a_0}^{-3\mathrm{}}$. This is compared with the theoretical values $0.786 {a_0}^{-3\mathrm{}}$ obtained by Callaway and $0.909 {a_0}^{-3\mathrm{}}$ obtained by a quantum defect calculation in this paper.