Experiments with intense laser suggest that light can stop electrons

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By hitting electrons with an ultra-intense laser beam, researchers at Imperial College have revealed dynamics that are said to ‘go beyond classical physics’ and to hint at quantum effects.

Whenever light hits an object, some of the light scatters back from its surface. However, if the object is moving extremely quickly and the light is incredibly intense, strange things can happen, according to the team. Electrons, for example, can be shaken so violently that they actually slow down because they radiate so much energy – something called a radiation reaction.

Radiation reaction is of interest to physicists studying effects beyond classical physics, as Maxwell’s equations are said to fall short in extreme environments.

The researchers were able to observe a radiation reaction by colliding an intense laser beam with a high-energy beam of electrons. The experiment was undertaken using the Gemini laser at the Science and Technology Facilities Council’s Central Laser Facility.

Senior researcher Dr Stuart Mangles from Imperial’s Department of Physics, said: “We knew we had been successful in colliding the two beams when we detected very bright high energy gamma-ray radiation.

“The real result then came when we compared this detection with the energy in the electron beam after the collision. We found these successful collisions had a lower than expected electron energy, which is clear evidence of radiation reaction.”

The data from the experiment is also said to be in better agreement with a theoretical model based on the principles of quantum electrodynamics, rather than with Maxwell’s equations. The researchers says this potentially provides some of the first evidence of previously untested quantum models.

More experiments will be conducted with an even higher intensity laser and higher energy electron beams to confirm the findings and these will be carried out later this year.