An ab initio investigation of the ground and first two excited electronic states of the difluoromethyl radical

Ab initio calculations have been performed to determine the structure and energies of the ground and first two excited electronic states of CHF2. The 6-31+G*, 6-311++G**, aug-ccpVDZ, and aug-cc-pVTZ basis sets were utilized at the MP2 and CCSD(T) levels of theory for the structures and energies of minima and transition states on the ground electronic surface. The 6-31+G*, 6-311++G** basis sets were utilized at the CIS, CASSCF, and MRCI levels of theory for characterization of the excited electronic states. The ground state was found to be pyramidal, the first excited state is possibly dissociative and the second excited state planar. Vertical transition energies for transitions from the ground to the first and second excited states were found to range from 61355 to 71372 cm(-1) at the CIS level of theory. Shallow local minima on the A state potential energy surface with long C-H bonds of about 2.0 Angstrom were located by using two-dimensional potential surface scans. Upon excitation to the h state, the C-H bond stays constant near 1.08 Angstrom, the C-F bond lengthens from 1.33 to 1.45 Angstrom, the H-C-F bond angle increases from 1140 to 1330, and the F-C-F angle decreases from 110degrees to 93degrees.