Numerical calculations of the optical gain due to short-wavelength transitions of helium-like ions in an optically thin plasma

A numerical calculation was made of the optical gain due to short-wavelength transitions of the helium-like ions Li⁺ (λ = 168 nm), C⁴⁺ (26.7 nm), and Al¹¹⁺ (4.59 nm) in an optically thin plasma. The cases of collisional and recombination pumping were investigated. The calculations were performed in terms of a multilevel model of a helium-like ion, in the quasisteady-state approximation, using refined values of the atomic constants and transition rates.