Thermoluminescence is a form of

luminescence Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment. A luminescent object emits ''cold light'' in contrast to incandescence, where an obje ...

that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from

electromagnetic radiation In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength ...

or other

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

is re-emitted as light upon heating of the material. The phenomenon is distinct from that of

black-body radiation Black-body radiation is the thermal radiation, thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific ...

Physics

High energy radiation creates electronic

excited state In quantum mechanics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Add ...

s in crystalline materials. In some materials, these states are ''trapped'', or ''arrested'', for extended periods of time by localized defects, or imperfections, in the lattice interrupting the normal intermolecular or inter-atomic interactions in the crystal lattice. Quantum-mechanically, these

state State most commonly refers to: * State (polity), a centralized political organization that regulates law and society within a territory **Sovereign state, a sovereign polity in international law, commonly referred to as a country **Nation state, a ...

s are

stationary state A stationary state is a quantum state with all observables independent of time. It is an eigenvector of the energy operator (instead of a quantum superposition of different energies). It is also called energy eigenvector, energy eigenstate, ene ...

s which have no formal time dependence; however, they are not stable energetically, as vacuum fluctuations are always "prodding" these states. Heating the material enables the trapped states to interact with

phonon A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. In the context of optically trapped objects, the quantized vibration mode can be defined a ...

s, i.e. lattice vibrations, to rapidly decay into lower-energy states, causing the emission of

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can ...

s in the process.

Use in dating

The amount of luminescence is proportional to the original dose of radiation received. In thermoluminescence dating, this can be used to date buried objects that have been heated in the past, since the ionizing dose received from

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

elements in the soil or from

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

s is proportional to age. This phenomenon has been applied in the thermoluminescent dosimeter, a device to measure the radiation dose received by a chip of suitable material that is carried by a person or placed with an object. Thermoluminescence is a common

geochronology Geochronology is the science of Chronological dating, determining the age of rock (geology), rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, ...

tool for dating

pottery Pottery is the process and the products of forming vessels and other objects with clay and other raw materials, which are fired at high temperatures to give them a hard and durable form. The place where such wares are made by a ''potter'' is al ...

or other fired archeological materials, as heat empties or resets the thermoluminescent signature of the material (Figure 1). Subsequent recharging of this material from ambient radiation can then be empirically dated by the equation: Age = (subsequently accumulated dose of ambient radiation) / (dose accumulated per year) This technique was modified for use as a passive sand migration analysis tool (Figure 2). The research shows direct consequences resulting from the improper replenishment of starving beaches using fine sands.

Beach nourishment Beach nourishment (also referred to as beach renourishment, beach replenishment, or sand replenishment) describes a process by which sediment, usually sand, lost through longshore drift or erosion is replaced from other sources. A wider beach c ...

is a problem worldwide and receives large amounts of attention due to the millions of dollars spent yearly in order to keep beaches beautified for tourists,Waikiki sand
/ref> e.g. in Waikiki, Hawaii. Sands with sizes 90–150 μm (very fine sand) were found to migrate from the swash zone 67% faster than sand grains of 150-212 μm (fine sand; Figure 3). Furthermore, the technique was shown to provide a passive method of policing sand replenishment and a passive method of observing riverine or other sand inputs along shorelines (Figure 4).

References

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{{Authority control Luminescence

Physics

Use in dating

References

Further reading

External links