Measurement of the Absolute Knight Shift in Lithium

We have measured the absolute Knight shift of ${\mathrm{Li}}^7$ in lithium metal by observing the ${\mathrm{Li}}^7$ nuclear resonance frequency as a function of conduction-electron paramagnetism. The latter was varied by saturating the conduction-electron spin resonance with microwave power. By using two slightly different techniques we obtain $K=243\mathrm{}\pm 10$ ppm and $K253\mathrm{}\pm 8$ ppm. Some of the difficulties and inherent uncertainties of the experiment are discussed in detail.