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# LULI2000 - Study of quantum interference effects in atomic populations of dense plasmas (F. Rosmej)

The atomic populations are the fundamental quantity for many different disciplines. They determine the radiative properties of matter including emission, absorption, scattering and the equation of state. They are of particular importance for applications like, e.g. in diagnostics (spectroscopy) and radiative losses. At present, the classical approach where atomic populations are calculated in the framework of a heuristically constructed model while atomic elementary processes are deduced from quantum mechanical calculations is currently widely spread in science and applications. In particular, this approach is almost exclusively employed in codes and diagnostic applications for hot plasmas and conventionally known as “Collisional-‐Radiative Model -‐ CRM”. The CRM ignores the fundamental quantum mechanical property of interferences of the wavefunctions Ψi: it keeps only the diagonal elements ΨiΨi * that are proportional to the populations while the non-‐diagonal ones ΨiΨj * are entirely ignored. Although the CRM has been the working horse in the plasma physics community since long, there are numerous cases where high precision spectroscopic data could not be satisfactorily explained. Our developments in the framework of the quantum atomic density matrix theory demonstrate that quantum interference effects on populations could be studied in dense plasmas with the help of the X-‐ray emission originating from autoionizing states of highly charged ions: these states are far from thermodynamic equilibrium even at high densities due to the large Auger rate. The purpose of the present experiment is a novel investigation of quantum interference effects on the atomic populations realized with the photon emission from He-‐like Lyman-‐alpha autoionizing states (dielectronic satellite transitions of highly charged Mg/Al/Si/Cl ions) studied via high-‐spectral and high-‐spatial resolution X-‐ray spectroscopy. Our density newly developed matrix calculations show large impact of quantum interference effects for certain satellite transitions that could be detected despite typical signal to noise ratios in ns-‐laser produced plasmas. In order to optimize quantum effects and to investigate their variations for different temperatures and densities and target elements, a variety of different plasma conditions (changing pulse lengths, energy, frequency, tamped and non-‐tamped targets) will be studied. Our simulations and preliminary experimental tests performed with aluminium plasmas demonstrate feasibility. The proposed experimental campaign will challenge state-‐of-‐the art CRM and provide benchmark data fundamental quantum studies in dense plasmas that go beyond the state-‐of-‐the-‐art.

**LULI2000** - S40-S41-S42/2020