Experimental observation of laser-stimulated radiative recombination

Spontaneous radiative recombination between protons and electrons to form hydrogen atoms with 8≤n≤19 has been measured. ${\mathrm{CO}}_2$ laser light has been shown to induce stimulated radiative recombination to the n=11 and 12 levels with an inferred gain in the cross section of 1720±860 and 4790±2830 for a laser power of 12.6 and 15.3 W, respectively. This is in line with that predicted theoretically.