title: Electronic spectra of H(2)C(2n)H+ radicals (n=2-6): an ab initio study.
abstract: The equilibrium geometries and vibrational frequencies of the carbon chain cations H(2)C(2n)H(+) (n = 2-6) in the X(1)A(1) ground states have been investigated by the DFT-B3LYP method. The structures of the X(1)A(1) and 2(1)A(1) electronic states for H(2)C(2n)H(+) (n = 2-5) have also been optimized by the CASSCF approach. The vertical excitation energies from the ground to selected excited states for H(2)C(2n)H(+) (n = 2-6) have been evaluated at the CASPT2/cc-pVTZ level. The studies reveal that the vertical excitation energies for the 2(1)A(1) <-- X(1)A(1) transitions are 4.56, 3.44, 2.75, 2.15 and 1.62 eV, respectively. For H(2)C(2n)H(+) (n = 2-4) molecules, our estimates are in reasonable agreement with the corresponding observed values of 4.34, 3.27 and 2.65 eV, respectively. In addition, the exponential-decay curves of these excitation energies are also suggested.
authors.affiliation: Institute of Theoretical Chemistry, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China.
authors.forename: Lihui
authors.initials: L
authors.lastname: Jiang
authors.forename: Chunzhang
authors.initials: C
authors.lastname: Wang
authors.forename: Junfeng
authors.initials: J
authors.lastname: Li
authors.forename: Xugeng
authors.initials: X
authors.lastname: Guo
authors.forename: Jinglai
authors.initials: J
authors.lastname: Zhang
mesh_terms: D004583:Electrons; D006838:Hydrocarbons / Q000737:chemistry*; D008956:Models, Chemical; D013057:Spectrum Analysis; D013816:Thermodynamics
chemical_list: D006838:Hydrocarbons