Lambdaemitted

Lambdaemitted is a term used to refer to the wavelength of photons emitted by a radiative transition in a light-emitting system, such as an atom, molecule, quantum dot, or luminophore. It corresponds to the emission line produced when electrons transition from an excited state to a lower-energy state.

Physically, lambdaemitted is related to the energy difference ΔE between the two states by ΔE = h c / λemitted, where h is Planck's constant and c is the speed of light. In practice the measured λemitted may differ from the exact transition energy due to environmental effects, Doppler broadening, and instrumental resolution.

Measurement and use: λemitted is determined by spectroscopy. Instruments such as spectrometers, monochromators, or spectrally resolving detectors are used. Accurate calibration against standards is essential; λemitted is typically reported in nanometers or other length units.

Examples and applications: Hydrogen's Balmer-α line at about 656.3 nm; sodium D-line at about 589 nm; the 632.8 nm line from a helium–neon laser. Emission wavelengths are fundamental in identifying species, characterizing materials, and designing light sources such as LEDs, lasers, and fluorescent probes.

Related concepts include the emission spectrum, fluorescence, phosphorescence, and quantum yield. In solid-state environments, confinement and crystal field effects can shift λemitted relative to free-atom values, a phenomenon known as spectral shift.