Theory of Natural Line Shape

  • Luiz Davidovich
  • H. M. Nussenzveig


The quantum-electrodynamical treatment of the emission of light by an atom has been strongly influenced by Weisskopf and Wigner’s early contribution(1) to this subject. While their work was highly successful in accounting for the observed line shape, several disturbing theoretical questions concerning the underlying assumptions remained unsettled:
  1. (i)

    An initial state for the system corresponding to an excited atomic eigenstate with no photons present was assumed, which seems quite unphysical. The state preparation and the dependence of the decay on the excitation should be discussed.

  2. (ii)

    It is well known that the exponential decay “ansatz” cannot be valid for all times, although deviations from it are expected to be extremely small for long-lived decaying states such as the atomic ones. However, the range of validity of the exponential decay law should be determined.

  3. (iii)

    The state space was restricted to a two-level atom and to the vacuum and one-photon sectors, without any indication of how to proceed in order to improve the approximation. For such a basic problem as this one, one should start from a clear-cut formulation, and a systematic procedure for deriving corrections to the Weisskopf-Wigner approximation should be given.



Wave Packet Line Shape Lamb Shift Transverse Electric Field Resonant Level 
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Copyright information

© Springer Science+Business Media New York 1980

Authors and Affiliations

  • Luiz Davidovich
    • 1
  • H. M. Nussenzveig
    • 2
  1. 1.Instituto de FísicaPontifícia Universidade Católica do Rio de JaneiroBrazil
  2. 2.Instituto de FísicaUniversidade de São PauloSão PauloBrazil

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