Vibronic coupling in asymmetric bichromophores: Experimental investigation of diphenylmethane-d5

摘要: Vibrationally and rotationally resolved electronic spectra of diphenylmethane-d 5 (DPM-d 5) are reported in the isolated-molecule environment a supersonic expansion. While small, asymmetry induced by deuteration one aromatic rings is sufficient to cause several important effects that change principle mechanism vibronic coupling between close-lying S1 S2 states, spectroscopic signatures such produces. The splitting origins 186 cm−1, about 50% greater than its value DPM-d 0 (123 cm−1), an amount bring zero-point level into near-resonance with v = 1 state low-frequency phenyl flapping mode, νR 191 cm−1. Dispersed fluorescence bear clear evidence Δv(R) Herzberg-Teller dominates near-resonant internal mixing manifolds. each pair Franck-Condon active ring modes shows suggests incorrectly states may be electronically localized. From studies, S0 have been well-fit asymmetric rotor Hamiltonians while perturbed not fit. transition dipole moment (TDM) orientation nearly perpendicular C2 symmetry axes 66(2)%:3(1)%:34(2)% a:b:c hybrid-type character origin contains 50(10)% a:c-type (S1) b-type (S2) character. A model put forward explains qualitatively TDM compositions dispersed emission patterns without need invoke localization. experimental data discussed here serve as foundation for multi-mode capable being applied bichromophores, presented work B. Nebgen L. V. Slipchenko [“Vibronic bichromophores: Theory application 5,” J. Chem. Phys. (submitted)].