1. Introduction
Thermoluminescence is the radiative recombination of electrons
and hole subsequent to thermal excitation of trapped electrons
and/or holes from shallow traps. Excitation of holes to the
valence band and/or excitation of electrons to the conduction band
are a non radiative process. Trapping sites must be relatively shallow
with respect to either the conduction or valence bands to allow
excitation by thermal energy. Deep traps will not release trapped
charges readily prior to thermal damage to the host material.
Recombination of electron/hole pairs can occur along four separate
routes after excitation: conduction band to valence band; conduction
band to hole trap; electron trap to valence band; or electron
trap to hole trap. Each of these recombination mechanisms will
have a different energy, radiating a different photon wavelength.
The radiated light is captured and analysed. Conventional TL measurements
simply measure the bulk intensity of light radiated. This
bulk light measurement is called a TL glow curve. Therefore TL
measurements can reveal the total number of charges trapped in
the material that radiatively recombined.
The luminescent materials are used as a radiation dosimeter for
personnel, environmental or clinical etc. dosimetry. As well as dose
response properties, stability and fading characteristics, the
knowledge of the kinetic parameters may provide some useful