Nickellike soft-x-ray lasing at the wavelengths between 14 and 7.9 nm

We report what we believe is the first observation of clear soft-x-ray lasing in Ni-like Ag, Te, La, Ce, and Pr and also in Nd covering the spectral range 14.3-7.9 nm. A curved slab target was irradiated with quadruple 1.053-microm laser pulses. The pulse-to-pulse separation for the first three pulses was 400 ps, and that between the third and the fourth pulses was 1.6 ns. The pulse duration and irradiance on the target were 100 ps and ~7 x 10(13) W/cm(2), respectively. For all the targets the most intense lasing was observed at the fourth pump pulse.