Efficient 2 S-3 positronium production by stimulated decay from the 3 P-3 level

We investigate experimentally the possibility of enhancing the production of 2 S-3 positronium atoms by driving the 1 S-3-3 P-3 and 3 P-3-2 S-3 transitions, overcoming the natural branching ratio limitation of spontaneous decay from 3 P-3 to 2 S-3. The decay of 3 P-3 positronium atoms toward the 2 S-3 level has been efficiently stimulated by a 1312.2 nm broadband IR laser pulse. The dependence of the stimulating transition efficiency on the intensity of the IR pulse has been measured to find the optimal enhancement conditions. A maximum relative increase of x (3.1 +/- 1.0) in the 2 S-3 production efficiency, with respect to the case in which only spontaneous decay is present, was obtained.