As an introduction to the subject of the talk, first we discuss „quantum optics with free electrons”, by showing that the minimal coupling with the quantized electromagnetic radiation naturally leads to the appearance of displaced (coherent) and squeezed states. On the basis of the exact analytic solutions of the Schrödinger or Dirac equations, we show that the transverse radiation aquires an effective mass, which is proportional with the plasma frequency. This circumstance plays an important role in various nonlinear processes, like the production of high-harmonics of an intense laser field, generation of attosecond pulses and the compensation of the so-called attochirp..


12. Juli 2024, 10:00-11:00


ZKS Uhrturmhörsaal
S2 08/171
Hochschulstraße 4

ZKS Uhrturmhörsaal , S2 08/171 , Hochschulstraße 4


Instiut für Angewandte Physik



Next, we extend the scope from the connection of quantum optics and plasmons to the electrodynamics of „genuine massive photons”, which may be described as Lánczos-Proca vector bosons with three ortogonal polatizations. Besides summarizing the basics of their history, we show the subtleties of emission and propagation of such vector bosons, and mention their relevance even in metrology.


In the third part of the talk we deal with the explanation of anomalous angular correlations at large relative angles of electron-positron pairs, stemming from the excited nuclear fusion products of reactions like 7Li(p,e+e-)8Be. This anomaly (in comparison with direct gamma decay accompanied with pair creation) has been explained by assuming the existence of a neutral boson, the “hypothetical X17 particle”, having an invariant mass around 17 MeV/c^2. This X17 boson would mediate energy and the necessary extra momentum from the decaying products. Recently we have taken the proton as the interacting charge in the Dirac equation, and, in order to find the exact solutions, we have used the same elimination technique mentioned above, which is based on the application of displacement and squeezing operators. With the help of these solutions we have derived an analytic formula, yielding the value 17.0087 MeV/c^2 for the invariant mass of the dressed radiation, which may be identified with the X17 particle as a vector boson. We note that, besides the Sommerfeld fine structure constant and the proton mass, the derived formula contains merely an elementaty statistical factor.

The present talk is a contribution to the Colloquium at TU Darmstadt honoring Prof. Dr. Gernot Alber 11-12. 07. 2024. The author dedicates this talk to Gernot with great pleasure and appreciation of his very broad scientific activity over decades, with many interesting and important results in the theory of light-matter interaction, quantum optics and quantum information science.



Kolloquium Institut für Angewandte Physik