Radiative properties of non-equilibrium nitrogen plasma in soft x-ray range
Soft X-ray emission at 2.3-3.0 nm region in nitrogen plasma can be observed mostly in 2p-1s and 3p-1s resonant transitions. Ions of nitrogen in plasma emitting in necessary band have a high energy excited state in comparison with plasma temperature in most experiments. Discharge and laser produced plasmas that are used in radiation sources often have non-equilibrium electron distributions with accelerated (high energy) electrons. In present work a kinetic modeling of such plasmas by collisional-radiative model is performed. Non-thermal electron distribution by the energy is used for calculations of impact processes rates on the basis of Hartree-Fock-Slater (HFS) quantum-statistical model and distorted wave approximation. It is shown that the presence of accelerated electrons in plasma at relatively small portions (0.1-1%) even may have a significant influence on the ion and level populations and the line emission intensities. It is found that the emission generation efficiency at specified range may be significantly increased.