The Ultimate Resolution Limit

  • Wolfgang Demtröder
Part of the Springer Series in Chemical Physics book series (CHEMICAL, volume 5)

Abstract

In Chap.10 several techniques have been presented which allow the Doppler width to be overcome. Provided that all other sources of line broadening could be eliminated, the spectral resolution of these techniques can reach at least in principle the limit imposed by the natural linewidth γn of a molecular transition. For allowed electronic transitions with typical natural linewidths of a few MHz, other broadening effects, such as pressure and power broadening or time-of-flight broadening (see Chap.3) can be indeed made smaller than the natural linewidth by an appropriate experimental arrangement. In such cases the natural linewidth has already been reached experimentally. On the other hand, there is much interest in ultrahigh resolution spectroscopy of lines with extremely small natural linewidths below the kHz range. Examples are visible or uv forbidden transitions between ground states and metastable excited states with long spontaneous lifetimes, or in the infrared region vibrational transitions between long-lived vibrational levels . For such transitions it is not the spontaneous lifetime but the finite interaction time of the molecules with the laser field which limits the spectral resolution. If the time of flight of a molecule passing through the laser beam is small compared with the spontaneous lifetime, the time-of-flight broadening becomes the major broadening mechanism, provided the laser frequency is sufficiently stable.

Keywords

Burning Magnesium Microwave Iodine Coherence 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1981

Authors and Affiliations

  • Wolfgang Demtröder
    • 1
  1. 1.Fachbereich PhysikUniversität KaiserslauternKaiserslauternFed. Rep. of Germany

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