Scientists have determined the colors of laser radiation, in which the helium atom is invisible. The results of the study are published by Science.

Physicists at the Australian National University have developed the most sensitive method for measuring the potential energy of an atom: within one hundredth of a decillionth of a joule, or 10-35 J. They used it to confirm quantum electrodynamics (QED). Recall that this is the quantum field theory of electromagnetic interactions, as well as the most developed part of quantum field theory.

The study, published this week in the journal Science, is based on determining the color of laser light, in which the helium atom is invisible. As the authors of the new work note, the experiment is an independent confirmation of previous methods used to test quantum electrodynamics. Among them is the measurement of transitions from one energy state of an atom to another.

“This invisibility is only for a certain atom and a certain color of light. Therefore, it cannot be used to make the invisibility cloak that Harry Potter used to explore the dark corners of Hogwarts, explains Bryce Henson, lead author of the new work, at the Australian National University Research School of Physics. “But we managed to explore some of the ‘back streets’ of QED theory.”

Using an extremely high-resolution laser and atoms cooled to 80 billionths of a degree above absolute zero (80 nanokelvins), the scientists achieved a sensitivity in energy measurements that was 5 orders of magnitude less than the energy of atoms, about 10-35 J.

“This is so small that I can’t think of a single phenomenon with which it could be compared,” the author of the study added.

Thanks to these measurements, scientists were able to deduce very accurate values ​​for the invisible color of helium. To compare their results with the theoretical prediction for QED, they turned to Professor Li-Yang Tang from the Chinese Academy of Sciences in Wuhan and Professor Gordon Drake from the University of Windsor in Canada. As a result, scientists achieved that the theoretical value was only slightly lower than the experimental one, and also 1.7 times higher than the experimental error.