Electronic spectra of linear isoelectronic species HC6H+, C6H, HC5N+
- 化学化工－已发表论文 
Multireference configuration interaction calculations have been used to determine term energies of low-lying doublet electronic states of isoelectronic carbon chains HC6H+, C6H and HC5N+. Calculations on relevant excited states in the energy range up to 6 eV show that (2)Pi and (2)Phi excited states due to the pi-pi excitation are comparable in energy pattern among such species, but that there are significant differences in the properties of (2)Sigma and (2)Delta excited state series of these isoelectronic species. Similarities and discrepancies are discussed based on molecular orbital energy patterns and electron correlation. The strongest transitions for HC6H+, C6H and HC5N+ are predicted to correspond to X(2)Pi -->2(2)Pi transitions at 2.22, 2.56 and 2.17 eV, respectively. For HC6H+, no (2)Sigma or (2)Delta states arising from sigma-pi electron promotion are found in the energy range up to 6 eV. However, in C6H the first excited state 1(2)Sigma (+) due to the 13 sigma -->3 pi excitation is found to be only slightly higher (0.22 eV) than the ground state X(2)Pi. Calculated transition energies in the present study show good agreement with available experimental results.