Optical Properties of Metal Alloys Determined by Wavelength - Modulated Derivative Spectroscopy.

Wavelength-modulated derivative spectroscopy has been used to give new insights into the optical properties of alloys which were unobtainable using conventional reflectivity techniques. New electronic circuitry has been developed, eliminating the old systems of mechanical servos and feedback loops, which increases the sensitivity of the spectrometer. A new technique has been developed for separating the intraband and interband contributions to the dielectric function which depends on the orthogonality of the functions describing the two parts. Interband assignments have been for (beta)'-AuZn which fix band gaps with much greater accuracy than was previously done. The Au d-bands are narrower than predicted by energy-band calculations as are most of the interband gaps. (beta)'-Cu(,x)Zn(,1-x) has been studied on both sides of the (beta)' (DBLARR) (alpha) + (beta)' phase transition. Significant changes in both the intraband and interband properties are seen as the transition is crossed. Changes in the fundamental absorption edge indicate that competing physical mechanisms account for the shifts in interband properties, shifts which are consistant with changes in the intraband properties. The shift in the interband absorption edge in (alpha) - Ag(,70)Zn(,30) is also included. With this amount of alloying the plasma resonance which dominants the spectrum of AG is eliminated. Observed shifts in interband absorption edge are consistent with a rigid-band interpretation for this degree of alloying.