Amplified spontaneous emission on the second xenon excimer continuum at 172 nm wavelength was observed in dense gas evaporated from a solid xenon surface and pumped by heavy ions. A pulsed 3.78 MeV Kr+ beam from a radio‐frequency quadrupole accelerator was used for the experiment. A series of 800 μJ particle pulses each 10 ns long was focused to a small, elliptical beam spot leading to a pump power density of the order of 1 GW/g. Optical gain in the target was deduced from the angular distribution of light emitted along the target axis, and from a variation of optical intensity with gain length. A maximum gain of 26%/cm was determined using a model calculation which reproduced the experimental data.