have different values. Mechanical work and reaction rates are
examples of path functions.
Path length: The distance in which light moves through a material.
Pauli exclusion principle: States that no two electrons can have the
same four quantum numbers.
Phonon: A quantum mechanical description of a special type of vibration, known as the normal modes in classical physics. Phonons
are the discrete amounts of energy crystalline structures that these
modes of vibration can absorb. In this aspect of quantized energy,
the phonon is analogous to the photon.
Phosphorescence: A relaxation process when an excited electron
undergoes nonradiative intersystem-crossing to a slightly more
stable excited state, called a triplet state, before relaxing and
releasing a photon of light.
Photobleaching (FRAP): Photobleaching is the process of destroying a
fluorophore with intense light. FRAP, or fluorescence recovery
after photobleaching, is the method quantifying lateral diffusion
rates by monitoring fluorescence under a microscope and measuring the time it takes for a photobleached segment of a
fluorophore film to reorganize. Fluorophores reorganize, intact
ones replacing the inactivated ones. The hole in fluorescence
created by photobleaching disappears at a rate determined by the
lateral diffusion.
Photodynamic therapy: A medical technique that involves killing targeted cells by exciting dyes and/or nanoparticles that are bound
to those cells.
Photorelaxation: Process of an excited state chromophore dissipating
energy through release of a photon.
Photovoltaic cell: A semiconductor device that captures energy from
light to produce an electric current, also known as a solar cell.
Physisorption: Process of exploiting weaker molecular forces to deposit
molecules on the surface. Generally weaker and less specific than
chemisorption.
Piezoelectric effect: An effect found in certain types of materials in which
applying mechanical force to the material (e.g., pushing or
pulling) induces an electric field in the material. The converse
450
Glossary
examples of path functions.
Path length: The distance in which light moves through a material.
Pauli exclusion principle: States that no two electrons can have the
same four quantum numbers.
Phonon: A quantum mechanical description of a special type of vibration, known as the normal modes in classical physics. Phonons
are the discrete amounts of energy crystalline structures that these
modes of vibration can absorb. In this aspect of quantized energy,
the phonon is analogous to the photon.
Phosphorescence: A relaxation process when an excited electron
undergoes nonradiative intersystem-crossing to a slightly more
stable excited state, called a triplet state, before relaxing and
releasing a photon of light.
Photobleaching (FRAP): Photobleaching is the process of destroying a
fluorophore with intense light. FRAP, or fluorescence recovery
after photobleaching, is the method quantifying lateral diffusion
rates by monitoring fluorescence under a microscope and measuring the time it takes for a photobleached segment of a
fluorophore film to reorganize. Fluorophores reorganize, intact
ones replacing the inactivated ones. The hole in fluorescence
created by photobleaching disappears at a rate determined by the
lateral diffusion.
Photodynamic therapy: A medical technique that involves killing targeted cells by exciting dyes and/or nanoparticles that are bound
to those cells.
Photorelaxation: Process of an excited state chromophore dissipating
energy through release of a photon.
Photovoltaic cell: A semiconductor device that captures energy from
light to produce an electric current, also known as a solar cell.
Physisorption: Process of exploiting weaker molecular forces to deposit
molecules on the surface. Generally weaker and less specific than
chemisorption.
Piezoelectric effect: An effect found in certain types of materials in which
applying mechanical force to the material (e.g., pushing or
pulling) induces an electric field in the material. The converse
450
Glossary