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Pure Appl. Chem.,
Vol. 68, No.12, pp. 2223-2286, 1996
Glossary of Terms Used in Photochemistry
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[D] [E] [F]
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JABLONSKI DIAGRAM
Originally, a diagram showing that the fluorescent state of a molecular
entity is the lowest excited state from which the transition to the
ground state is allowed, whereas the phosphorescent state is a metastable
state below the fluorescent state, which is reached by radiationless
transition. In the most typical cases the fluorescent state is the
lowest singlet excited state and the phosphorescent state the lowest
triplet state, the ground state being a singlet. Presently, modified
Jablonski diagrams are frequently used and are actually state diagrams
in which molecular electronic states, represented by horizontal lines
displaced vertically to indicate relative energies, are grouped according
to multiplicity into horizontally displaced columns. Excitation and
relaxation processes that interconvert states are indicated in the
diagram by arrows. Radiative transitions are generally indicated with
straight arrows (), while radiationless transitions are generally
indicated with wavy arrows  .
JAHN-TELLER EFFECT
For nonlinear molecular entities in a geometry described by a point
symmetry group possessing degenerate irreducible representations there
always exists at least one nontotally symmetric vibration that makes
electronically degenerate states unstable at this geometry. The nuclei
are displaced to new equilibrium positions of lower symmetry causing
a splitting of the originally degenerate states. This effect is due
to the odd terms in the vibronic perturbation expansion.
See also Renner-Teller
effect.
[A] [B] [C]
[D] [E] [F]
[G] [H] [I]
[J] [K] [L]
[M]
[N] [O] [P]
[Q] [R] [S]
[T] [U] [V]
[W] [X] [Y]
[Z]
Page last modified 31 August 2000.
Copyright ©1999 International Union of Pure and Applied Chemistry.
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