Glossary of Terms Used in Photochemistry
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VALENCE BAND
The highest energy continuum of energy levels in a semiconductor that
is fully occupied by electrons at 0 K.
See bandgap energy,
conduction band,
Fermi level.
VAVILOV RULE
See Kasha-Vavilov rule.
VERTICAL TRANSITION
See Franck-Condon principle.
VIBRATIONAL REDISTRIBUTION
Intramolecular redistribution of energy among the vibrational modes
usually giving a statistical distribution of their populations, characterized
by the "vibrational temperature". For large molecules, this process
does not require collisions.
VIBRATIONAL RELAXATION
The loss of vibrational excitation energy by a molecular entity through
energy transfer to the environment caused by collisions. The molecular
entity relaxes into vibrational equilibrium with its environment.
See relaxation.
VIBRONIC COUPLING
Interaction between electronic and vibrational motions in a molecular
entity.
See Jahn-Teller
effect and Renner-Teller
effect.
VIBRONIC TRANSITIONS
A transition which involves a change in both the electronic and vibrational
quantum numbers of a molecular entity, as opposed to purely electronic
or purely vibrational transition. The transition occurs between two
states, just as in a purely electronic transition, but involves a
change in both electronic and vibrational energy.
