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Fluorescence microscopy relies upon fluorescent compounds, or fluorophores, in order to image biological systems.Since fluorescence and phosphorescence are competitive methods of relaxation, a fluorophore that undergoes intersystem crossing to the triplet excited state no longer fluoresces and instead remains in the triplet excited state, which has a relatively long lifetime, before ...
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 fluorescents.
Jablonski diagram indicating intersystem crossing (left) and internal conversion (right). Internal conversion is a transition from a higher to a lower electronic state in a molecule or atom. [ 1 ] It is sometimes called "radiationless de-excitation", because no photons are emitted.
However, sustained excitation is followed by intersystem crossing to the triplet state (3 A) that relaxes to the ground state by phosphorescence with much longer decay times. In simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light.
Intersystem crossing, an excited state dynamic in chemistry and physics; Iron–sulfur cluster biosynthesis protein family, machinery for producing iron–sulfur ...
Triplet states typically have longer lifetimes than excited singlets. The prolonged lifetime increases the probability of interacting with other molecules nearby. Photosensitizers experience varying levels of efficiency for intersystem crossing at different wavelengths of light based on the internal electronic structure of the molecule. [2] [7]
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.
However, the 1 T 1 excited state has a very short lifetime, decreasing the probability for the excited state to relax via a double intersystem crossing to reach the 5 T 2 HS state . [3] Since the HS state is spin forbidden the lifetime for this state is long, therefore it can be trapped at low temperatures.