that the molecule drops from a higher-energy state to a lower one.
Fluorescence and phosophorescence are emission processes.
Enthalpy: Heat transferred in an isobaric process.
Entropy: A state function representing the possible number of configurations available to a system or to the surroundings. Systems with
more states available are less ordered and have energy spread out
over more states.
Evanescent field: Standing waves formed at the boundary between
two media with different wave motion properties. They decay
exponentially with distance from the boundary in which the
waves are formed.
Excitation transfer: Transfer of energy from one molecule to another
(e.g., one drops to a lower energy quantum state and the other is
excited to a higher energy quantum state).
Exciton: A “quasiparticle” consisting of one or more excited electrons
and unfilled orbitals (holes) that are electrostatically bound to
each other. Excitons can diffuse through a system and can absorb
light at different wavelengths than individual electrons depending
on how strongly they are bound and whether they are oscillating
in-phase or out-of-phase.
Extensive property: A thermodynamic variable (e.g., mass or volume)
that is proportional to the size of the system.
Extinction coefficient: Also called molar absorptivity, it is a parameter
that helps define how strongly a substance absorbs light. It is often
given at a given wavelength per mass unit or per molar concentration. The extinction coefficient is proportional to the imaginary
component of the material’s refractive index.
Ferroelectric: A material that has a permanent electric dipole moment
(e.g., a positively charged surface and a negatively charged
surface) analogous to a permanent magnet. Ferroelectric materials are non-centrosymmetric.
Field-effect transistor: A semiconductor device that allows current to
pass between two electrodes when a voltage is applied to a third
electrode, causing the energy levels of states in the region
between the electrodes to shift.
442
Glossary
Fluorescence and phosophorescence are emission processes.
Enthalpy: Heat transferred in an isobaric process.
Entropy: A state function representing the possible number of configurations available to a system or to the surroundings. Systems with
more states available are less ordered and have energy spread out
over more states.
Evanescent field: Standing waves formed at the boundary between
two media with different wave motion properties. They decay
exponentially with distance from the boundary in which the
waves are formed.
Excitation transfer: Transfer of energy from one molecule to another
(e.g., one drops to a lower energy quantum state and the other is
excited to a higher energy quantum state).
Exciton: A “quasiparticle” consisting of one or more excited electrons
and unfilled orbitals (holes) that are electrostatically bound to
each other. Excitons can diffuse through a system and can absorb
light at different wavelengths than individual electrons depending
on how strongly they are bound and whether they are oscillating
in-phase or out-of-phase.
Extensive property: A thermodynamic variable (e.g., mass or volume)
that is proportional to the size of the system.
Extinction coefficient: Also called molar absorptivity, it is a parameter
that helps define how strongly a substance absorbs light. It is often
given at a given wavelength per mass unit or per molar concentration. The extinction coefficient is proportional to the imaginary
component of the material’s refractive index.
Ferroelectric: A material that has a permanent electric dipole moment
(e.g., a positively charged surface and a negatively charged
surface) analogous to a permanent magnet. Ferroelectric materials are non-centrosymmetric.
Field-effect transistor: A semiconductor device that allows current to
pass between two electrodes when a voltage is applied to a third
electrode, causing the energy levels of states in the region
between the electrodes to shift.
442
Glossary