Superradiant Line in the Soft—X-Ray Range

Abstract

It is shown that the $2{p}^{5}4d^{3}P_{1}\ensuremath{\rightarrow}2{p}^{6}^{1}S_{0}$ line of the ${\mathrm{Al}}^{3+}$ ion at a wavelength of 117.41 \AA{} is superradiant in a dense laser-produced plasma. The measured gain in a two-plasma experiment is 17%. The gain coefficient is of the order of 10 ${\mathrm{cm}}^{\ensuremath{-}1}$ with a lower limit of 2.5 ${\mathrm{cm}}^{\ensuremath{-}1}$ and an upper limit of 22 ${\mathrm{cm}}^{\ensuremath{-}1}$.