X-ray laser on transitions of Pd-like ions from ErXXIII to ReXXX

The wavelengths, the rates of processes, and the gains of spontaneous emission at the transitions of Pd-like ions from ErXXIII to ReXXX are calculated for the first time. The high quantum yield of amplified emission in these ions is possible at transitions in the spectral range from 10 to 16 nm. It is assumed that a plasma is produced due to the interaction of an ultrashort laser pulse with a beam of clusters, dust or nanotubes of one of the eight elements from Er to Re. Laser action in such experiments can appear at two transitions: at the 4d⁹5d [J = 0] — 4d⁹5p [J = 1] transition, for which the population inversion mechanism is similar to the mechanism existing at the 0 — 1 transition in Ne- and Ni-like ions; and at the 4d⁹5f [J = 1] — 4d⁹5d [J = 1] transition, for which the population inversion is produced due to the reabsorption of photons. Optimal conditions are determined for achieving the most efficient short-wavelength lasing for the specified geometry of a plasma filament of a homogeneous density. It is shown that the conversion efficiency of the pump pulse energy to the soft X-ray energy in the range from 10 to 16 nm exceeds 10% for all the ions studied.