The biexcitonic quenching and exciton migration rate in aromatic crystals

Parametric interactions and nonlinear Raman processes of vibronic excitons in polydiacetylene studied with a two‐optical‐cycle laser

“…1 Introduction It has been well known that the lifetimes of molecular excited states and Frenkel excitons are reduced under high-density excitation in aromatic molecular crystals such as anthracene [1,2], pyrene [3], fluoranthene [4], a charge-transfer complex [5], J aggregates [6], and polymers [7][8][9][10][11]. The mechanism of the lifetime shortening is well established to be the Auger process, in which one of two neighboring excitations (excited molecules or Frenkel excitons) are excited to a higher excitation (higher electronic excited state in a molecule or an excited exciton state) and the other to the ground state by the transition dipole-transition dipole interaction [1][2][3][4].…”

“…The mechanism of the lifetime shortening is well established to be the Auger process, in which one of two neighboring excitations (excited molecules or Frenkel excitons) are excited to a higher excitation (higher electronic excited state in a molecule or an excited exciton state) and the other to the ground state by the transition dipole-transition dipole interaction [1][2][3][4]. The higher excitations are expected to relax very rapidly to the lowest excited state or the lowest exciton state, resulting in the shortening of the lifetime of the excitations [4,5,8,9].…”

Sum and difference frequency mixing of molecular vibrations in a polymer under high-density optical excitation

“…[7][8][9][10][11] The mechanism of the lifetime shortening is well established to be the Auger process, in which one of two neighboring excitations ͑excited molecules or Frenkel excitons͒ is excited to a higher excitation ͑higher electronic excited state in a molecule or an excited exciton state͒ and the other to the ground state by the transition-dipole-transition-dipole interaction. [1][2][3][4] The higher excitations are expected to relax very rapidly to the lowest excited state or the lowest exciton state, resulting in the shortening of the lifetime of the excitations. 4,5,8,9 It has not been possible to time resolve the fast relaxation process from the higher excited state generated by the Auger mechanism to the lowest excited singlet state, which includes both electronic relaxation ͑internal conversion͒ and vibrational relaxation.…”

“…[1][2][3][4] The higher excitations are expected to relax very rapidly to the lowest excited state or the lowest exciton state, resulting in the shortening of the lifetime of the excitations. 4,5,8,9 It has not been possible to time resolve the fast relaxation process from the higher excited state generated by the Auger mechanism to the lowest excited singlet state, which includes both electronic relaxation ͑internal conversion͒ and vibrational relaxation. The Auger process followed by the relaxation processes has been considered to be nearly instantaneous or beyond the time resolution of the apparatus utilized in the experiments.…”

“…[13][14][15] At high-density excitation, the decay becomes faster and it cannot be fitted to a single exponential function, 16 but can be fitted to the analytic solution including both mono-and bimolecular decay terms. [1][2][3][4]17 When bimolecular quenching of singlet excitons takes place, the time behavior of the exciton density n is expressed by…”