Mid-Infrared (Mid-IR)

Related terms

Chromophore

The molecular subunit responsible for a dye's colour, typically a conjugated double-bond system; chemical erasure destroys the chromophore while leaving the decolourised...

Ionising Radiation

Electromagnetic radiation whose photon energy exceeds the ionisation potential of atoms (typically above ~10 eV); includes gamma rays and X-rays. UV below...

Photon

A quantum of electromagnetic radiation; a discrete energy packet with energy E = hν where h is Planck's constant and ν is...

Photon Energy (eV)

Photon energy expressed in electron volts; UV photons carry 3-12 eV (chemically reactive), visible 1.8-3.1 eV, mid-IR 0.05-0.5 eV (vibrational excitation only).

Planck-Einstein Equation

E = hν = hc/λ; relates photon energy to frequency and wavelength. Foundation of all spectral energy calculations.

Refractive Index

A physical property of glass (and other transparent materials) that describes how much light bends when passing through it. Forensic glass comparison...

Soret Band

The intense porphyrin absorption band of haemoglobin at 415 nm; the spectral basis for bloodstain contrast enhancement.

UV-a

The ultraviolet band from 315 to 400 nm; the primary band used for UV-reflectance forensic imaging of bruises, GSR, and bite marks...

UV-C

Ultraviolet radiation in the 100-280 nm band; the 254 nm germicidal line excites biological-fluid fluorescence in forensic screening.

Wave-Particle Duality

The quantum-mechanical property of electromagnetic radiation: it behaves as a wave (diffraction, interference, polarisation) and as a stream of photons (photoelectric effect,...

Wavenumber (Cm^-1)

Reciprocal of wavelength in centimetres, the standard unit for mid-infrared spectra; 1 cm^-1 = 10^7 / λ(nm).

Explained in

• Light, Photons and the Forensic EM SpectrumThe 2500-25000 nm (400-4000 cm^-1) spectral region where functional-group vibrational absorptions serve as chemical fingerprints; the operating region of FTIR...