Study in Physical Review Letters Journal Reveals Rare Light Amplification in Helium
A team from the Department of Low and Medium Energy Physics from the Jožef Stefan Institute (Janez Turnšek et all), investigated how helium atoms behave when excited by intense, finely tuned extreme ultraviolet light pulses. Normally, helium atoms in certain excited states release their energy by emitting an electron through a process called autoionization. Only a tiny fraction of atoms in such states emit a photon - roughly one in 1600. In their experiment at the FERMI free-electron laser in Trieste, the researchers passed high-intensity extreme ultraviolet pulses through a pressurized column of helium gas to amplify this extremely weak emission. Through a process called amplified spontaneous emission or ASE, the faint fluorescence was boosted into a bright beam of 40.74 eV photons. At higher gas pressures, Turnšek and colleagues also observed shifts in the emitted light’s wavelength, pointing to new effects like 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.
