The location, polarization and assignment of low lying excited triplet states in pyrene

It is concluded that the T-n <- T-1 absorption spectrum in the visible and near infrared is due to four electronic transitions, for which the 0-0 transitions are located at 10 300, approximate to 16300. 19 200 and 24 200 cm(-1). They are assigned to the B-3(3g)+ <- B-3(2u)+. (3)A(g)(+) <- B-3(2u)+, B-3(3g)- - B-3(2u)+ and (3)A(g)(-) <- B-3(2u)+ transitions respectively. The B-3(3g)+ state is shown to be situated only 400 +/- 100 cm(-1) above the first excited singlet state. which may explain the reported temperature dependent part of the intersystem crossing rate.