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5479720 
Journal Article 
The π→π* excited states of long linear polyenes studied by the CASCI-MRMP method 
Kurashige, Y; Nakano, H; Nakao, Y; Hirao, K 
2004 
Yes 
Chemical Physics Letters
ISSN: 0009-2614 
400 
4 
425-429 
Multireference Møller–Plesset perturbation theory with complete active space configuration interaction (CASCI-MRMP) is applied to the study of the valence π→π* excited states of all-trans linear polyenes C2nH2n+2 (n=3–14). Our focus was to determine the nature of the four lowest-lying singlet excited states, 21Ag-,11Bu+,11Bu-and31Ag- and their ordering. The ionic 11Bu+ state is the lowest optically allowed excited state, while the covalent 21Ag-,11Bu-and31Ag- states are the optically forbidden states. Theory predicts that the 11Bu- state becomes lower than the 11Bu+ state at n⩾7 and that the 31Ag- state also becomes lower than the 11Bu+ state at n⩾11.