Theoretical investigation of the spectrum and conversion efficiency of short wavelength extreme-ultraviolet light sources based on terbium plasmas

The emission spectrum and conversion efficiency of laser-produced terbium plasmas are theoretically investigated on the basis of computational atomic data. The theoretically calculated spectrum reproduces the main peak of observed spectrum at λ=6.5 nm, which originates from 4d−4f transitions of near palladiumlike ions (Tb19+). A simple model of the isothermal expansion of terbium plasma suggests that efficient emission can be achieved by pumping the plasma with a laser pulse at an intensity of approximately one order of magnitude greater than that used with tin sources at λ=13.5 nm.