Population inversion and gain calculations for 4p54d-4p55p and 4p55s - 4p55p Kr-like transitions in Y IV, Zr V, Nb VI and Mo VII

We present calculations of the quasi-steady state gain coefficient for the 4p54d 1P-4p55p 1/2[1/2]0 transition in Kr-like Y IV, Zr V, Nb VI and Mo VII ions. Gain coefficients which can lead to FUV-VUV (∝260 to 60 nm) lasing are found in all ions. Large gain coefficients are found for each ion at temperatures in excess of the ion's equilibrium temperature; realizing lasing in these systems will require a transient excitation mechanism. The density at which the maximal gain coefficient obtains increases for increasing ionization state. The 4p55s 1/2[1/2]1-4p55p 1/2[1/2]0 and 4p55s 3/2[3/2]1-4p55p 1/2[1/2]0 transitions also show population 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 transition as well as the case with which they are produced in a low temperature, table-top scale plasma source. (orig.)