Study in Physical Review Letters Journal Reveals Rare Light Amplification in Helium
Janez Turnšek and the team from the Jožef Stefan Institute, together with collaborators from Italy, investigated how helium atoms behave when excited by intense, finely tuned light pulses. Normally, helium atoms in certain excited states release their energy invisibly through autoionization, with only a tiny fraction—about one in 1600—emitting a photon. In their experiment at the FERMI free-electron laser in Trieste, the researchers passed high-intensity laser pulses through a pressurized column of helium gas to amplify this extremely weak emission. Remarkably, the faint fluorescence was boosted into a measurable beam of 63.67 eV photons directed along the laser path, confirming theoretical predictions. At higher gas pressures, Turnšek and colleagues also observed shifts in the emitted light’s wavelength, pointing to new effects from electron scattering and atomic interactions. Their results not only validate cutting-edge models but also open new opportunities to explore how matter interacts with intense light fields in regimes that were previously inaccessible.
