Atomic Absorption Spectra

  • The concept of atomic absorption spectra is based on the principle that atoms can absorb specific frequencies of light.
  • Atom’s electrons can only exist in fixed energy levels. When the atom absorbs light (energy), the electrons jump to a higher energy level.
  • Each element has its own unique set of energy levels, which leads to each element having a unique atomic absorption spectrum.
  • The spectrum of an atom is a series of coloured lines against a dark background. The bright lines are the visible light frequencies that an atom emits when its electrons fall back to their normal energy levels.
  • In the context of astronomy, astronomers analyse the atomic absorption spectra of light from stars and other heavenly bodies to determine which elements are present.
  • The concept of “red shift” - the change in colour of light from stars moving away from us towards the red end of the spectrum - is dependent on an understanding of atomic absorption spectra. It is a key piece of evidence for the Big Bang theory.
  • An atomic absorption spectrum acts like a ‘fingerprint’ for an element, as no two elements have the same spectrum.
  • By examining the absorption spectrum from a distant star, we can determine the chemical composition, temperature, radial velocity, and many more physical properties of that particular star.