Researchers of the Department of Low and Medium Energy Physics at Jožef Stefan Institute: Janez Turnšek, Klemen Bučar, Andrej Mihelič, Špela Krušič and Matjaž Žitnik, report new experimental results in Physical Review Letters. Upon passage of intense resonant XUV light of the free-electron laser FERMI through millimeters thick helium gas at a few tens of millibars pressure, self-amplification of weak spontaneous decay from doubly excited state has been observed at the EIS-TIMEX beamline. Due to stimulated emission, the fraction of excited atoms emitting an XUV photon instead of an electron has significantly increased significantly. The effect of decay redirection together with the collimation of emitted light leads to 8 orders of magnitude larger number of XUV photons emitted in the forward direction. This result provides opportunity to test new theoretical models and encourages further research to improve the efficiency of XUV spectroscopy and contribute to the development of new coherent light sources at short wavelengths.