Atomic spectrum

An atomic spectrum is the pattern of wavelengths emitted or absorbed when atoms undergo transitions between electronic energy states. Its discrete lines reflect the atom’s quantized energy levels.

Atomic energy levels: The discrete allowed energies of an atom’s electrons, set by its interactions and quantum state. A spectral line’s wavelength records the energy difference between two levels.
Quantum mechanics: The physical theory describing matter and radiation at atomic and subatomic scales. Its rules account for discrete atomic states and the transitions that generate spectra.
Joseph von Fraunhofer: A German optician and physicist who mapped dark lines in the solar spectrum in the early nineteenth century. His precise line measurements established a foundation for systematic spectroscopy.
Spectroscopy: The study of how matter interacts with electromagnetic radiation as a function of wavelength or frequency. Atomic spectra are a central source of information in spectroscopic analysis.
Molecular spectrum: A pattern of wavelengths produced or absorbed through transitions in molecules. Molecular spectra include vibrational and rotational structure absent from isolated-atom spectra.
Photon: A quantum of electromagnetic radiation carrying energy and momentum. An atomic transition emits or absorbs a photon whose energy matches the level spacing.
Electromagnetic radiation: Energy that propagates through space as coupled electric and magnetic fields. Atomic spectra are observed as wavelength patterns in emitted or absorbed radiation.
Gustav Kirchhoff: A German physicist who formulated laws relating emission and absorption spectra to matter. His experiments showed that elements produce characteristic spectral lines.
Kirchhoff's laws of spectroscopy: Rules describing the continuous, emission-line, and absorption-line spectra produced by hot, dense, and cooler gases. They explain why the same element can create bright or dark lines in different settings.
Continuous spectrum: Radiation spread across an uninterrupted range of wavelengths. Its smooth range contrasts with the discrete lines characteristic of atoms.

Linked from 22 pages