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Photons have no charge. Light is a form of electromagnetic energy.

All spectroscopic effects (to my knowledge) are due to changes in electron state, induced either through an interior or exterior EM (Electro-Magnetic) field. EM forces may affect that state, which in turn affects the light emitted during the change of state, e.g. the Zeeman effect, etc.

However, if we exclude all such spectroscopic phenomena, and consider EM fields purely energetically on the one side, and light energy on the other, are there any know direct effects of EM fields on light itself?

(I'd really like to hear from physicists with hands on knowledge - and please keep all the Tags as is because I have reasons for selecting them, thx.)

Howard Pautz
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Quantum electrodynamics does predict scattering of light on light, but this effect is small and has not been observed experimentally, AFAIK. Scattering of electromagnetic radiation in the Coulomb field of nuclei was, however, observed (http://en.wikipedia.org/wiki/Delbr%C3%BCck_scattering )

akhmeteli
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I have an example in mind that may satisfy your curiosity. It is a Nature paper you can find here:

It describes a scenario in which the EM intensity is so high that electron-positron pairs are created, whose subsequent annihilation generate additional photons. This translates in a non-linearity in the Maxwell equations which give rise to an interference pattern typical of double-slit experiments.

Mattia
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