70 research outputs found
人総研シンポジウム抄録 : 福島原発事故12年の経験から学ぶ -当時小学生だった若者達との対話から(第2回)-
departmental bulletin pape
Intrinsic Analysis of Radiative and Room-Temperature Nonradiative Processes Based on Triplet State Intramolecular Vibrations of Heavy Atom-Free Conjugated Molecules toward Efficient Persistent Room-Temperature Phosphorescence
The radiative rate (<i>k</i><sub>p</sub>) of the lowest triplet excited state (T<sub>1</sub>)
and the nonradiative rate based on intramolecular vibrations at room
temperature [<i>k</i><sub>nr</sub>(RT)] from T<sub>1</sub> for heavy atom-free conjugated structures are determined by considering
the triplet yield and quenching rate from T<sub>1</sub>. Donor substitution
did not strongly influence <i>k</i><sub>nr</sub>(RT) but
greatly enhanced <i>k</i><sub>p</sub>. The <i>k</i><sub>nr</sub>(RT) values were comparable between donor-substituted
molecules and nonsubstituted molecules, which we explain by similar
vibrational spin–orbit coupling (SOC) related to the transition
from T<sub>1</sub> to the ground state (S<sub>0</sub>). We attribute
the enhancement of <i>k</i><sub>p</sub> induced by donor
substitution to the appearance of a large SOC between high-order singlet
excited states (S<sub>m</sub>) and T<sub>1</sub> together with the
large transition dipole moments of the S<sub>m</sub>–S<sub>0</sub> transitions. Knowledge of this mechanism is important for
developing future efficient persistent room-temperature phosphorescence
from doped aromatic materials and aromatic crystals
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