The total absence of any heat; -273oC 0 Kelvin.
A small amount of an element added to a very pure chemical to bestow luminescent properties.
The emission of light from a phosphor after the excitation has ceased.
a Particle. These are Helium nuclei (two neutrons plus two protons). They are a product of radioactivity but only penetrate a few centimetres in air due to their high charge.
A luminescent process that does not obey Stokes law. e.g. The excitation wavelength is longer than the emission wavelength.
b Particle. A high-energy electron created when a neutron turns into a proton within a radioactive nucleus; it is negatively charged.
Another term for Beta particles
Long UV from a very dark blue glass tube or bulb (Wood’s glass)
A theoretical material that when heated to incandescence will emit radiation according to Planck’s equation. The colour of the emission moves from deep red through orange, white and finally blue-white with increasing temperature.
Black Body Curve
A curve on the chromaticity diagram connecting the colour points of black bodies at increasing Kelvin.
The natural colour of a material in daylight
The symbol for the velocity of light. ~ 3×108 m/sec
Charge-Coupled Device; an array of light-sensitive electronic detectors.
A unit of luminous intensity defined as the brightness of a black body, at the temperature of the solidification of Platinum, is 60 candela cm-1.
An ion has either a positive or a negative charge
The addition of an extra ion, which enables an activator ion to enter a crystal lattice when it does not have the correct charge. e.g. Cu+ in Zn2+ in ZnS:Cu:Cl
A chart that permits the definition of colours using x and y co-ordinates.
Commission Internationale d’Eclairage. 1931. An International body that standardised the definition of colour in 1931. It uses x y co-ordinates on a chromaticity diagram.
The conjunction of the x y co-ordinates of a phosphor.
The ability of a light source to accurately reflect the colours of an object.
Colour Rendering Index
A scale of colour rendering ability; 100% is perfect colour rendering. Tri-chromatic phosphor lamps achieve about 85% CRI.
The definition of near white colours using K. e.g. 3000 K warm white, 3500 K white and 4500 K daylight.
The incorporation of an activator into a host by precipitating them simultaneously from a mixed solution.
Cathode Ray Tube.
Crystal Field Effect
The effect of the surrounding crystal lattice on the activator of a phosphor. Substitution with similar ions can cause subtle changes or shifts on emissions. e.g. Mg, Ca, Sr, Ba.