Spectroscopic and theoretical studies of novel germanium-carbon and mixed germanium-silicon-carbon clusters

Abstract

Fourier transform infrared (FTIR) studies coupled with density functional theory (DFT) calculations have been initiated on a new family of molecular clusters containing germanium-carbon (Ge n C m ) and mixed germanium-silicon-carbon (Ge l Si n C m ) which are formed by laser ablation and trapped in solid Ar ? 10K. The determination of the ground-state geometries and vibrational fundamentals for these new molecular species is facilitated by a comparison of measured fundamental frequencies, isotopic shifts, and intensities with the predictions of the DFT calculations, which is being carried out in concert with the experimental work. Of particular interest are comparisons with previously reported ground-state geometries and fundamental vibrations for a large number of related silicon-carbon (Si n C m ) and pure carbon (C n ) clusters. Both Ge n C m and Ge l Si n C m clusters have a potential semiconductor importance. The successful optical characterization of these new molecular species called for a refinement of the laser ablation technique. As a result of this work a reliable and reproducible method was found to fabricate and laser ablate highly enriched 13 C samples. This new found method has aided in the identification of five new molecular species, and has promising implications for future studies for carbon-bearing species. The ? 3 (? u ) mode of linear GeC 3 Ge, the first optical observation of a Ge n C m clusters, has been assigned at 1920.7 cm ?1 . The ? 1 (?) mode linear GeC 3 Si, the first-ever synthesis and identification of a Ge l Si n C m species, has been assigned at 1939.0 cm ?1 . The optical characterization of other Ge n C m clusters include the ? 1 (?) mode linear GeC 7 , the ? 1 (?) mode linear GeC 4 , and the ? 4 (?) mode linear GeC 9 assigned at 2063.6, 2093.3, and 1928.3 cm ?1 , respectively. All results are in good agreement with the DFT predictions.