III. Formation of Carbon Clusters 2317 IV. Thermodynamic Properties 2319 V. C2 2319 A. Structure and Spectroscopy 2319 B. C2 2320 C. C2 2321 VI. C3 2321 A. Early Experimental Work 2321 B. Mid-IR and Far-IR Spectroscopy 2321 C. Electronic Spectroscopy 2323 1. The Σu + Ground State 2323 2. The AΠu State 2324 3. The Σu + State 2324 4. The aΠu and bΠg States 2325 5. Other Band Systems 2326 D. C3 in the Interstellar Medium 2326 E. C3 2326 F. C3 2327 VII. C4 2327 A. Theory 2327 B. Experiment 2328 1. The Rhombic Isomer 2328 2. The Linear Isomer 2328 C. Excited Electronic States 2330 D. C4 2331 E. C4 2332 VIII. C5 2332 A. Theory 2332 B. Experiment 2332 C. Excited Electronic States 2334 D. C5 2334 E. C5 2335 IX. C6 2335 A. Theory 2335 B. Experiment 2336 1. The Cyclic Isomer 2336 2. The Linear Isomer 2336 C. Excited Electronic States 2337 D. C6 2338 E. C6 2338 X. C7 2338 A. Theory 2338 B. Experiment 2338 C. Excited Electronic States 2340 D. C7 2340 E. C7 2340 XI. C8 2341 A. Theory 2341 B. Experiment 2342 1. The Cyclic Isomer 2342 2. The Linear Isomer 2342 C. Excited Electronic States 2342 D. C8 2342 E. C8 2342 XII. C9 2343 A. Theory 2343 B. Experiment 2343 C. Excited Electronic States 2345 D. C9 2345 E. C9 2345 XIII. C1

http://www.cchem.berkeley.edu/rjsgrp/publications/papers/1998/200_orden_1998.pdf

Small carbon clusters: spectroscopy, structure, and energetics.

The structure and energetics of the ring isomers of C(4n+2) (n=3-5) carbon clusters were studied by using coupled-cluster singles and doubles excitation theory to overcome the vast differences existing in the literature The results obtained in the present study clearly indicate that C(14), C(18), and C(22) carbon rings have bond-length and bond-angle alternated acetylenic minimum energy structures Contrarily, density functional theory calculations were unable to predict these acetylenic-type structures and they ended up with the cumulenic structures It is found from the coupled-cluster studies that the lowest-energy ring isomer for the first two members of C(4n+2) series is a bond-angle alternated cumulenic D((2n+1)h) symmetry structure while the same for the remaining members is a bond-length and bond-angle alternated C((2n+1)h) symmetry structure In C(4n+2) carbon rings, Peierls-type distortion, transformation from bond-angle alternated to bond-length alternated minimum energy structures, occurs at C(14) carbon ring

/pdf/ccsd-calculations-on-c14-c18-and-c22-carbon-clusters-156av5frw2.pdf

CCSD calculations on C14, C18, and C22 carbon clusters

The surface plasmon polariton-enhanced Raman spectra of size-selected C16, C18, and C20 clusters isolated in nitrogen matrices are presented along with the calculated vibrational frequencies for the ring and linear chain isomers. The Raman spectra, recorded at a range of excitation wavelengths from 457.9 to 670 nm, show strong resonance enhancement for the three clusters. The calculated vibrational frequencies for ring and linear chain isomers and the cage and bowl structures for C20 are compared to the experimental frequencies. Systematic shifts in the series of peaks in the 200 cm−1 region for C16, C18, and C20 suggest that the observed isomers have the same geometry, thereby ruling out the bowl and cage isomers for C20. The measured spectra appear to be most consistent with the linear chain isomer. This high-energy isomer may be produced during neutralization of the deposited cluster ions.

/pdf/raman-spectra-and-calculated-vibrational-frequencies-of-size-48kjmna8s2.pdf

Raman spectra and calculated vibrational frequencies of size-selected C16, C18, and C20 clusters

Rhomboidal SiC 3

The cyclic C6 cluster has been identified for the first time in Fourier transform infrared spectra of the products from the laser evaporation of graphite rods trapped in Ar at ∼10 K. Measurements on spectra produced using both 12C- and 13C-enriched rods combined with the results of new density functional theory calculations performed in the present work as well as previous calculations by Martin and Taylor, have resulted in the assignment of the most intense infrared active mode, ν4(e′)=1694.9 cm−1 of the cyclic C6 isomer with D3h symmetry. This assignment is based on excellent agreement of the frequency, 13C isotopic shifts, and relative intensities with the theoretical predictions.

Detection of cyclic carbon clusters. II. Isotopic study of the ν12(eu) mode of cyclic C8 in solid Ar

The first germanium–carbon cluster GeC3Ge, has been detected in the products from the laser evaporation of carbon and germanium rods trapped in solid Ar at ∼10 K On the basis of very good agreement between Fourier transform infrared (FTIR) measurements and the predictions of density functional theory (DFT) calculations for the frequencies and 13C isotopic shifts, the ν3(σu) mode of linear GeC3Ge has been identified at 19207 cm−1

Vibrational spectra of germanium–carbon clusters. I. Identification of the ν3(σu) mode of linear GeC3Ge

Experimental and theoretical studies of a novel family of germanium–carbon clusters (GenCm) that were initiated with our earlier identification of the GeC3Ge cluster have now been extended to the GeC7 and GeC9 chains. The new clusters, which were formed by laser ablation and trapped in solid Ar at ∼10 K, have been identified using Fourier-transform infrared (FTIR) measurements coupled with density-functional theory (DFT) calculations. The ν1(σ) vibrational fundamental of linear GeC7 has been identified at 2063.6 cm−1, and an absorption at 1928.3 cm−1 has been assigned to the ν4(σ) fundamental of linear GeC9. FTIR measurements of the isotopic shifts for the assignments are in good agreement with the DFT predictions.

Vibrational spectra of germanium–carbon clusters. II. GeC7 and GeC9

A Fourier transform infrared study has resulted in the first observation of a vibrational spectrum of the linear SiCCH radical produced by trapping the products of the vacuum ultraviolet photolysis of a mixture of SiH4 silane, and C2H2 acetylene, in an Ar matrix at 10 K Two fundamentals have been observed, the ν2(σ), carbon–carbon stretching mode at 19898 cm−1 and the ν3(σ), silicon–carbon stretching mode at 6360 cm−1 The frequency of the 19898 cm−1 band and the results of extensive measurements of D and 13C isotopic shifts are in good agreement with the predictions of new CCSD(T) (coupled cluster with single, double, and triple excitations) ab initio calculations for the ν2 mode, while the assignment of the 6360 cm−1 band is considered somewhat less certain

Fourier transform infrared observation of the vibrational spectrum of the linear SiCCH radical in Ar at 10 K

The first optical observation of a mixed germanium-silicon-carbon (GelSimCn) cluster has been made by trapping the products of the laser ablation of carbon/silicon/germanium rods in Ar at 10 K. The ν1(σ) C–C stretching mode of linear GeC3Si has been identified at 1939.0 cm−1. The assignment is confirmed by the very good agreement between Fourier transform infrared (FTIR) measurements of frequencies and isotopic shifts and predictions of our quantum theoretical calculations.

C. M. L. Rittby

Papers

Detection of cyclic carbon clusters. II. Isotopic study of the ν12(eu) mode of cyclic C8 in solid Ar

Vibrational spectra of germanium–carbon clusters. I. Identification of the ν3(σu) mode of linear GeC3Ge

Vibrational spectra of germanium–carbon clusters. II. GeC7 and GeC9

Fourier transform infrared observation of the vibrational spectrum of the linear SiCCH radical in Ar at 10 K

Identification of the ν1(σ) mode of linear GeC3Si