A Theoretical Study on the Excited States of the KCCH Radical

Based on the C2v symmetry, the low-lying electronic states of the KCCH radical was studied in the complete active pace self-consistent field (CASSCF) and multi-configurational second-order perturbation theory (CASPT2) methods. For the low-lying electronic states of KCCH, the calculated harmonic vibrational modes are in agreement with theoretical reports. Moreover, the electron transitions of KCCH, from X1Σ+ to 21Σ+, 11Π, 21Π, 11Σ-, 13Σ+, 13Π, 23Π and 13Σ-, are predicted at 5.43, 5.59, 7.87, 5.50, 5.15, 5.73, 5.53 and 6.82 eV, respectively. The CASSCF/CASPT2 potential energy curves (PECs) were calculated for K+-loss dissociation from the 13Σ+, 23Σ+,13Π ,21Σ, 11Π and 21Π states. Analyses of electron transition and dissociation curves show the ionic properties in the metal–ligand bond for KCCH. The dissociation energy of the KCCH (X1Σ+)→CCH-(11Σ)+K+(S0) is 4.423 eV at the CASSCF/CASPT2 level