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Universität zu Köln
Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

Practical Course M: Isotopic Shift in the Spectra of Hydrogen and Deuterium

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Isotopic shift is the change of electronic energy states of atoms and molecules with an isotopic substitution. For light atoms this shift is maily caused by the change in mass of the atomic nucleus (mass effect), whereas for heavier atoms the change in the number of neutrons also causes a change in the charge distribution of the atomic nucleus, which gives rise to a shift in the energy levels of the electrons (volume effect). In general, also the different nuclear spins of isotopes contribute to the isotopic shift.

The isotopic shift of energy levels of hydrogen compared to deuterium are explained well by the mass effect. The shift is relatively large (1-2 Å) and can already be detected using medium resolution.


The tutorial may be downloaded here in PDF format or alternatively be obtained personally from the assistant.


Dr. Netty Honingh – Room 315 – Tel: 470-4528
Email: honingh (at)

Recommended reading

  • M. Born and E. Wolf. Principles of Optics. Cambridge University
  • W. Demtröder. Laser Spektroscopy. Springer
  • B. Cagnac and J. C. Pebay-Peyroula. Modern atomic Physics. Macmillan
  • W. Demtröder. Atoms, Molecules and Photons: An Introduction to Atomic-, Molecular- and Quantum-Physics. Springer
  • M. Klein. Optics. J.Wiley&Sons