Quantum Deflection Unraveled

Physics 16, s114
Improved calculations of a quantum phenomenon called Delbrück scattering resolve a long-standing discrepancy between theory and experiment.
J. Sommerfeldt/Technical University of Braunschweig

The sky owes its color to a process known as Rayleigh scattering, in which light bounces off electrons bound to atoms. Quantum physics permits an analogous effect, dubbed Delbrück scattering, whereby photons deflect from the electrostatic field around atomic nuclei. Now Jonas Sommerfeldt at the Technical University of Braunschweig, Germany, and his colleagues present highly accurate calculations of this quantum deflection [1]. The results should aid the analysis of nuclear photon-scattering experiments that could increase knowledge of nuclear structure.

According to quantum theory, empty space is not actually empty but teeming with particle–antiparticle pairs that flit in and out of existence. Delbrück scattering occurs when photons interact with such pairs in the electrostatic field of a nucleus. The probability that this process happens is encoded in a quantity called the Delbrück cross section. In the case of heavy nuclei, the values of this quantity obtained from theoretical calculations have disagreed with those extracted from experimental data for at least half a century.

Sommerfeldt and his colleagues developed a way to compute the Delbrück cross section that is accurate for a wide range of photon energies and nuclei. The key innovation is the use of a mathematical function that can account for typically neglected contributions to the cross section. As a demonstration, the researchers applied their technique to the Delbrück scattering of high-energy photons by plutonium nuclei. Unlike previous calculations, this one returned a cross section that matches the experimental value, thus resolving the aforementioned discrepancy. The team says that this computational method should enable sensitive tests of quantum electrodynamics—the fundamental theory describing how light and matter interact.

–Ryan Wilkinson

Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.


  1. J. Sommerfeldt et al., “All-order Coulomb corrections to Delbrück scattering above the pair-production threshold,” Phys. Rev. Lett. 131, 061601 (2023).

Subject Areas

Quantum PhysicsNuclear PhysicsParticles and Fields

Related Articles

First Direct Detection of Electron Neutrinos at a Particle Collider
Particles and Fields

First Direct Detection of Electron Neutrinos at a Particle Collider

Electron neutrinos produced by proton–proton collisions at the LHC have been experimentally observed. Read More »

Dark Matter Could Bring Black Holes Together

Dark Matter Could Bring Black Holes Together

Dark matter that interacts with itself could extract significant momentum from a binary supermassive black hole system, causing the black holes to merge. Read More »

Nuclear Decay Detected in the Recoil of a Levitating Bead
Nuclear Physics

Nuclear Decay Detected in the Recoil of a Levitating Bead

A levitating microparticle is observed to recoil when a nucleus embedded in the particle decays—opening the door to future searches of invisible decay products. Read More »

More Articles