Calculation of Davydov Splitting of the First Triplet State in Pyrene

Abstract

The Davydov splitting of the first triplet state of crystalline pyrene has been calculated for three different molecular orbital π‐electron wavefunctions. It is found that the contribution to the splitting from charge transfer states is an order of magnitude larger than that due to neutral exciton states. With an estimated value of $\text{0.25± 0.05}$ for the square of the (0, 0) vibrational overlap integral, the calculated Davydov splitting of the zero vibrational component of the first triplet state is between 1 and 2 cm⁻¹. The B_u state is found to be primarily b polarized. These results compare favorably with the measured splitting of $\text{2.4± 0.6\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ with the b polarized state at higher energy.