Absorption spectra of mercury and cadmium in solid rare gases

Abstract

The ultraviolet absorption spectra of mercury and cadmium in solid rare gases were obtained on a 2.2-meter vacuum spectrograph. Rare gas to metal atom molar ratios of 20:1 to 650:1 were used at formation temperatures of 16.3 to 30.0°K. The electronic transitions investigated were the 2536Å line of mercury (6^3 P_1 - 6^1 S_0) and the 2288Å line of cadmium (5^1 P_1 - 5^1 S_0 ). The absorption spectra of the metal atoms in xenon exhibited multiplets. These multiplets were explained by assuming one component caused by isolated atoms and other components caused by atoms at nonnearest-neighbor sites in the solid. The energies of the interacting pairs were obtained from diatomic potential curves of Hg2 and Cd2. The assignment of the isolated component was confirmed in the case of cadmium by selective bleaching of components. The energy differences obtained from the diatomic potential curves are Within 10% of those obtained experimentally. Mercury absorption spectra were also obtained in argon and krypton. The absorption spectra of mercury in krypton displayed poorly resolved spectra that were explained in the same manner as mercury in xenon. The absorption spectra of mercury in argon displayed two wide bands that were explained by assuming one band was caused by isolated atoms and atoms at nonnearest-neighbor sites in the solids; the other components a:te caused by mercury dimers. The relative areas of these bands were found to be dependent on temperature of the matrix. This temperature dependence was explained by assuming that the strength of the argon lattice diminishes with increase in temperature, hence, increasing the chances of dimer formation.