Fourier transform far infrared spectroscopy of the ν′3 vibration of SiC2 in Ar at 10 K

Abstract

A Fourier transform study of the vibrational spectrum of SiC2 produced by vaporizing mixtures of silicon and carbon-12 or carbon-13 at 2900 K and quenching the products in argon at 10 K, has enabled the identification for the first time of the ν″3(b2) vibrational mode, which the results of an earlier matrix study had suggested should lie in the far infrared. The assignment of a frequency observed at 160.4 cm−1 to the ν″3 mode is confirmed by isotopic data and supported by the predictions of ab initio calculations. Optimized force constants have been derived using the frequencies of the newly assigned mode, the previously reported, ν″1(a1)=1741.3 and ν″2(a1)=824.3 cm−1 vibrations, and their values on single and double carbon-13 substitution. Two models, cyclic and T-shaped, are discussed for the molecule, which is of C2V symmetry.

Theoretical identification of the lowest-energy structure of (SiC)12 heterocluster: Segregation of C and Si in planar and cage structures

“…The calculated bond angle of 39.976°for the SiC 2 triangle is in excellent agreement with the experimental angle of 40.4° [40]. The calculated vibrational frequencies 182.2, 760.3, and 1784.9 cm À1 are also in agreement with the experimental data of 160.4, 824.3, and 1741.3 cm À1 [42]. Hence we believe that the BLYP functional and DND basis set used here would reproduce the general features of the SiC nanostructures.…”

Toward resolution of the silicon dicarbide (SiC2) saga: Ab initio excursions in the web of polytopism

“…Discovery of the 3 0 1 transition 487 cm Ϫ1 above the band origin ended longstanding confusion and sparked further reassignment of the à 1 1 B 2 vibronic structure, while a joint analysis of the 3 1 1 hot band revealed that 3 Љϭ196.37 cm Ϫ1 , or 36 cm Ϫ1 above its argon matrix counterpart. 19 The DF spectra proved to be rich sources of vibrational term energies for the The vibrational analyses of SiC 2 culminated in a 1994 collaboration between Ross and the Sandia group. 33 Stimulated emission pumping ͑SEP͒ of the X 1 A 1 /à 1 B 2 system was implemented to dissect the (0,0, 3 Љ) manifolds for 3 Љ ϭ2, 4, 6, 12, and 14 with full rotational resolution, providing a collection of 11-15 J K a K c levels for each of these largeamplitude bending states.…”

“…)ϭ837 rather than 852 cm Ϫ1 for the ground state. Finally, in a 1990 investigation 19 the highly anharmonic 3 (b 2 ) vibration was located directly for the first time in the far-infrared region by FTIR spectroscopy, appearing in argon matrices at 160.4, 157.7, and 155.3 cm Ϫ1 for 28 Si 12 C 2 , 28 Si 12 C 13 C, and 28 Si 13 C 2 , respectively. A Jacobitype force field was found to provide the most favorable fit to the isotopomeric frequency data, consistent with a T-shaped molecule exhibiting a nondirectional Si-C 2 bond.…”

“…16 The compilation of definitive spectroscopy on SiC 2 continued with renewed matrix-isolation Fourier transform infrared experiments. [17][18][19] In 1985 Shepherd and Graham 17 observed that only four new symmetric stretching fundamental bands result from 13 C substitutions, viz., 1 (C-C str.) at ͑1708, 1674͒ cm Ϫ1 and 2 (Si-C str.)…”

Vibrational spectra of tetra-atomic silicon–carbon clusters. I. Rhomboidal Si3C in Ar at 10 K

“…4) and Si 2 C (Ref. 6) were observed to be the most abundant species, although weak bands ofSiH 2 , SiH 4 , and SiN 2 provided indirect evidence of the presence of atomic Si.…”