Die optischen Konstanten des Kaliums und die Theorie von Drude
The results of new measurements of the optical constantsn andk of the alkali metal K, performed in ultrahigh vacuum on mirrorlike surfaces free of any contamination and distortion in the wavelength region from 0·365 μ to 2 μ at temperatures between −183° C and +85° C were compared with the predictions of the Drude-theory. This permits the following main conclusions:1.The relation forn2-k2≡ε (real part of the metal's dielectric constant) derived by Drude proves to be valid; therefore, the total polarisation 4πNα (α=polarizability) of the metal remains small compared with 1 and the interband absorption has no influence on it.2.The quotientN/m, N beeing the number of conduction electrons andm the electronic mass has been determined, permitting either the calculation of the effective numberNeff of conduction electrons or of the effective optical massmeff,opt. Within the limits of experimental error both quantities prove to be independent of temperature between −183° C and +85° C.3.The critical wavelengthλc corresponding to the plasma frequencyνc was found to be equal toλc=2909 Å (hνc=4·25 eV).