Relaxation of Ne^(1+)1s^(0)2s^(2)2p^(6)np produced by resonant excitation of an ultraintense ultrafast x-ray pulse

The creation and relaxation of double K-hole states 1s^(0)2s^(2)2p^(6)np(n≥3)of Ne^(1+)in the interaction with ultraintense ultrafast x-ray pulses are theoretically investigated.The x-ray photon energies are selected so that x-rays first photoionize1s^(22)s^(22)p^(6) of a neon atom to create a single K-hole state of 1s2s^(22)p^(6) of Ne^(1+),which is further excited resonantly to double K-hole states of ls^(0)2s^(2)2p^(6)np(n≥3).A time-dependent rate equation is used to investigate the creation and relaxation processes of 1s^(0)2s^(2)2p^(6)np,where the primary microscopic atomic processes including photoexcitation,spontaneous radiation,photoionization and Auger decay are considered.The calculated Auger electron energy spectra are compared with recent experimental results,which shows good agreement.The relative intensity of Auger electrons is very sensitive to the photon energy and bandwidth of x-ray pulses,which could be used as a diagnostic tool for x-ray free electron laser and atom experiments.

Detailed Theoretical Investigations on the L-Shell Absorption of Open-M-Shell Germanium Plasmas:Effect of Autoionization Resonance Broadening

Radiative opacity of open-M-shell germanium plasmas in the L-shell photon energy region were investigated in detail by using a fully relativistic detailed level accounting approach. Among other physical effects such as relativistic and the interaction between fine-structure levels belonging to the same non-relativistic configuration and different configurations, particular attention is paid on the effect of autoionization resonance broadening on the L-shell absorption. The results show that for plasmas at present and past typical experimental conditions, line width due to autoionization resonance broadening dominate among all the physical broadening mechanisms including electron impact and Doppler broadenings. Such an effect is most pronounced for ions with just a few 2p-nd transition lines such as Ge14+, while it is not so pronounced for complex ions such as Ge16+, where there are so many 2p-nd lines that line overlapping partly conceal the effect of autoionization resonance broadening. After taking the effect of autoionization resonance broadening into account, detailed comparisons are made with available experimental spectra at different physical conditions of different plasma temperatures and densities. The L-shell absorption is sensitive to the plasma temperature, especially in the 2p-3d excitation energy region. The potential of utlizing the relative shape and intensity of the 2p-3d spin-orbit splitting as temperature diagnostics is investigated.

Electron localization enhanced photon absorption for the missing opacity in solar interior

The internal solar structure predicted by the standard solar model disagrees with the helioseismic observations even by utilizing the most updated physical inputs, such as the opacity and element abundances. By increasing the Rosseland mean, the decade-old open problem of the missing opacity can be resolved. Herein, we propose that the continuum electrons in the radiative processes lose phases and coherence as matter waves, giving rise to a phenomenon of transient spatial localization. It not only enhances the continuum opacity but also increases the line widths of the bound-bound transitions. We demonstrate our theoretical formulation by investigating the opacity of solar mixtures in the interior. The Rosseland mean demonstrates an increase of 10%-26% in the range of 0.3 R⊙-0.75 R⊙. The results are compared with the recent experimental data and the existing theoretical models. Our findings provide novel clues to the open problem of the missing opacity in the solar interior and new insight on the radiative opacity in the hot dense-plasma regime.