Quantum chemical calculations of formyl radicals

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Abstract
The ground state (2 A′) of the fluoroformyl radical, FCO, has been investigated by the unrestricted Hartree-Fock method. Pulay's force method for open-shell systems has been applied to calculate the complete quadratic force field and the diagonal cubic force constants. The force relaxation method has been used to determine the equilibrium geometry of FCO: . Adjusting the diagonal force constants to the observed vibrational frequencies of 19F12C16O and taking the values for the off-diagonal force constants from the UHF calculations, the force field of FCO is found to be: . This force field is compared with experiment and with the force fields of HCO, H2CO, and F2CO. The ground state of the FCO+ ion is calculated to be linear with R CO = 1·105 Å and R CF = 1·233 Å. As in HCN and FCN, substitution of H by F changes the sign of the stretch-stretch coupling constant.