The Uncertain Energy of an Excited State


This paper asks an experimental question about photon absorption and emission in a two-state electronic system where the incident frequency of exciting light is below the mean frequency of the emission line but still within the line width. Since it is well known that the absorption spectrum and the emission spectrum are identical [1]-[3], then quantum mechanics as well as astronomical observations say that excitations will still occur. Once a quantum state excites, then it is expected to decay back with a typical time constant and the usual emission spectrum. The problem is that the mean frequency of that emission spectrum will then be higher than the frequency of the exciting photon, suggesting that more energy is emitted than being received on average. A search of quantum mechanical references finds no discussion of this issue, so this paper considers the options available to resolve this inconsistency, including an experiment.

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Hutchin, R. (2015) The Uncertain Energy of an Excited State. Optics and Photonics Journal, 5, 201-204. doi: 10.4236/opj.2015.56019.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Sharma, A. and Schulman, S.G. (1999) Introduction to Fluorescence Spectroscopy. John Wiley & Sons, Chichester.
[2] Emission and Absorption Spectra. Department of Physics, University of Illinois.
[3] Line Width and Line Shape.
[4] Einstein, A. (1917) Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation). Physika Zeitschrift, 18, 121-128.
[5] Wineland, D.J. and Dehmelt, H. (1975) Proposed 1014Δν < ν Laser Fluorescence Spectroscopy on Tl + Mono-Ion Oscillator. Bulletin of the American Physical Society, 20, 637.
[6] Wineland, D.J., Drullinger, R.E. and Walls, F.L. (1978) Radiation-Pressure Cooling of Bound Resonant Absorbers. Physical Review Letters, 40, 1639.

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