GENERATION OF COHERENT IR, VISIBLE AND UV RADIATIONS BY TWO-PHOTON PUMPING IN ATOMIC BARIUM M. TALEB, G. FABRE, R. STRINGAT, J. d'INCAN et C. EFFANTIN J. Phys. Colloques, 48 C7 (1987) C7-577-C7-579 DOI: 10.1051/jphyscol:19877137