Autoionization-Pumped Laser

Doubly excited autoionizing states in barium of the configuration $6p_{\frac{3}{2}}\mathrm{np}$ ($n>~12$) are shown to decay preferentially to yield the $6p_{\frac{1}{2}}$ excited state of ${\mathrm{Ba}}^{+}$. The resulting population inversion is used to produce amplified spontaneous emission at 493 and 650 nm corresponding to the $6p_{\frac{1}{2}}-6\mathrm{}{s}_{\frac{1}{2}}$ and $6p_{\frac{1}{2}}-5\mathrm{}{d}_{\frac{3}{2}}$ transitions in ${\mathrm{Ba}}^{+}$. This principle of selective autoionization is expected to be applicable to the construction of a new class of ion lasers extending into the vacuum-ultraviolet wavelength region.