Search results
Results from the WOW.Com Content Network
For efficient TTA upconversion, the sensitizer should absorb strongly in the desired excitation range and have high conversion efficiency from the singlet excited state to the triplet excited state. [9] The emitter should have a singlet energy level just below twice the energy of the first triplet excited state.
Singlet and triplet energy levels. When a singlet state nonradiatively passes to a triplet state, or conversely a triplet transitions to a singlet, that process is known as intersystem crossing. In essence, the spin of the excited electron is reversed.
A Jablonski diagram showing the excitation of molecule A to its singlet excited state (1 A*) followed by intersystem crossing to the triplet state (3 A) that relaxes to the ground state by phosphorescence. It was used to describe absorption and emission of light by fluorescence.
Singlet fission is a spin-allowed process, unique to molecular photophysics, whereby one singlet excited state is converted into two triplet states.The phenomenon has been observed in molecular crystals, aggregates, disordered thin films, and covalently-linked dimers, where the chromophores are oriented such that the electronic coupling between singlet and the double triplet states is large.
The singlet-singlet transition between the two excited states is spin-allowed but parity-forbidden. The lower, O 2 (1 Δ g) state is commonly referred to as singlet oxygen. The energy difference of 94.3 kJ/mol between ground state and singlet oxygen corresponds to a forbidden singlet-triplet transition in the near-infrared at ~1270 nm. [12]
Triplet quenchers such as butadiene solvents can be used to increase stereospecific yields. [9] Halogenated solvents also stabilize the singlet state. [ 2 ] [ 7 ] For example, dibromomethane and hexafluorobenzene deactivate the higher-energy singlet state, [ 9 ] decelerating the rate of intersystem crossing in accordance with earlier studies of ...
2 molecule, the spins of the two hydrogen nuclei (protons) couple to form a triplet state known as orthohydrogen, and a singlet state known as parahydrogen. The triplet orthohydrogen state has total nuclear spin I = 1 so that the component along a defined axis can have the three values M I = 1, 0, or −1.
The ability of positronium to form both singlet and triplet states is described mathematically by saying that the product of two doublet representations (meaning the electron and positron, which are both spin-1/2 doublets) can be decomposed into the sum of an adjoint representation (the triplet or spin 1 state) and a trivial representation (the ...