Superradiant Line in the Soft—X-Ray Range

Abstract

It is shown that the $2p^{5}4d{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\to 2p^6{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ line of the ${\mathrm{Al}}^{3+}$ ion at a wavelength of 117.41 Å 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 ${\mathrm{cm}}^{-1\mathrm{}}$ with a lower limit of 2.5 ${\mathrm{cm}}^{-1\mathrm{}}$ and an upper limit of 22 ${\mathrm{cm}}^{-1\mathrm{}}$.