ABSORPTION-SPECTRA OF TELLURIUM CLUSTERS IN SOLID ARGON

Tellurium clusters (Te2, Te3, and two structural isomers of Te4) have been prepared by passing tellurium vapor through an argon microwave discharge and condensing the effluent onto a 12 +/- 2 K cold sapphire window. The Te2 diatomic and two isomers of Te4 have also been prepared by passing tellurium vapor through a superheater (800-degrees-C) followed by condensing with excess argon at 12 +/- 2 K. Absorption bands at 400 and 440 nm were identified as Te2, and the forbidden X2 <-- X1 transition between spin-orbit components of the 3SIGMA(g)- ground state of Te2 was observed in the infrared spectrum at 1984.3 cm-1. A structured absorption band centered at 665 nm is assigned to Te3, which is in agreement with the resonance Raman excitation profile. Two absorption bands in the near-infrared region (an unstructured band at 760 nm and a structured band centered at 960 nm) were interconverted upon selective photolysis with band-pass filters. These two bands are assigned to structural isomers of Te4 similar to those observed for S4 and Se4. New infrared bands at 243, 232, and 224 cm-1 are assigned to the 760-, 665-, and 960-nm absorbing species, respectively, on the basis of their similar photolysis and annealing behaviors.