The spectrum-resolved radiant energies in the 0.1–1.6 keV range from various plane targets irradiated by a 0.53-μm laser at 0.1–1.0-nsec pulses with intensities of ${10}^{13}$–2×${10}^{15}$ W/${\mathrm{cm}}^2$ are obtained. The conversion efficiency increases with the laser-pulse duration. The physical meaning of the obtained spectrum, such as the correspondence between the emitted photons and the responsible plasma density and temperature region, is clarified from the computational studies by using the one-dimensional hydrodynamic Lagrangian code which is coupled with a nonlocal thermodynamic equilibrium average ion model and multigroup radiation transport. The energy transport of the absorbed laser energy is discussed. Atomic-number dependences of the obtained spectrum and x-ray conversion efficiency show an undulatory structure. This is well reproduced qualitatively and to some extent quantitatively by the code calculation and the contributions of the electronic transitions in different orbital shells are approximately estimated.

• Received 6 August 1985

DOI:https://doi.org/10.1103/PhysRevA.33.525