6533b837fe1ef96bd12a1fd5
RESEARCH PRODUCT
Equilibrium Geometry of the Ethynyl (CCH) Radical
Jeppe OlsenMihály KállayJürgen GaussPéter G. SzalayLea Thøgersensubject
Quantum chemicalChemistryComputational chemistryThermodynamicsPhysical and Theoretical ChemistryEquilibrium geometryIsotopomersdescription
The equilibrium geometry of the ethynyl (CCH) radical has been obtained using the results of high-level quantum chemical calculations and the available experimental data. In a purely quantum chemical approach, the best theoretical estimates (1.208 A for r C C and 1.061-1.063 A for r C H ) have been obtained from CCSD-(T), CCSDT, MR-AQCC, and full CI calculations with basis sets up to core-polarized pentuple-zeta quality. In a mixed theoretical-experimental approach, empirical equilibrium geometrical parameters (1.207 A for r C C and 1.069 A for r C H ) have been obtained from a least-squares fit to the experimental rotational constants of four isotopomers of CCH which have been corrected for vibrational effects using computed vibration-interaction constants. These geometrical parameters lead to a consistent picture with remaining discrepancies between theory and experiment of 0.001 A for the CC and 0.006-0.008 A for the CH distances, respectively. The corresponding r S and r 0 geometries are shown not to be representative for the true equilibrium structure of CCH.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2004-02-17 |