Population inversion and gain calculations for 4p(5)4d-4p(5)5p and 4p(5)5s-4p(5)5p Kr-like transitions in YIV, ZrV, NbVI and MoVII

We present calculations of the quasi-steady state gain coefficient for the 4p(5)4d P-1-4p(5)5p 1/2[1/2](0) transition in Kr-like Y IV, Zr V, Nh VI and Mo VII ions. Gain coefficients which can lead to FUV-VUV (similar to 260 t o 60 nm) lasing are found in all ions. Large gain coefficients are found fo r each ion at temperatures in excess of the ion's equilibrium temperature; realizing lasing in these systems will require a transient excitation mecha nism. The density at which the maximal gain coefficient obtains increases f or increasing ionization state. The 4p(5)5s 1/2[1/2](1)-4p(5)5p 1/2[1/2](0) and 4p(5)5s 3/2[3/2](1)-4p(5)5p 1/2[1/2](0) transitions also show populati on inversion and modest gain coefficients Attractive features of these ions as potential lasents are the large ratio between the energy of the lasing transition and the excitation energy of the upper level of the lasing trans ition as well as the ease with which they are produced in a low temperature , table-top scale plasma source.