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Lineshifts at atomic pressures dataset

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posted on 2025-05-14, 13:17 authored by Gilbert CollinsGilbert Collins

At atmospheric pressures the atom is typically considered immutable with known energy levels for electrons, however in the deep interiors of stars where atoms exist at and beyond the atomic unit of pressure, i.e. hundreds of millions to billions of atmospheres pressure, the atom is fundamentally changed. At such conditions, unbound electrons are squeezed interior to core orbitals of the atom, screening the nuclear charge and dramatically shifting the quantum energy levels for electrons. The plasma becomes integral to the structure and properties of the atom, a regime that is challenging for today’s theoretical tools and where benchmark data are needed. We present the first such data: time resolved measurements of the inner most electron bound-bound transitions, for highly–ionized chromium with pressures up to 10 billion atmospheres (1 petapascal) and temperatures ≈ 400 eV. These results reveal a shortcoming in ab-initio density functional theory modeling of atomic structure and radiative transitions at these extreme conditions. Moreover, a measured 20-eV shift in the x-ray absorption lines together with a simple atomic physics model provides the first constraints for screening effects on atomic orbitals at and beyond atomic pressures. This shift is consistent with a charge of 0.17e (0.005e) penetrating the 2p (1s) orbit for Cr.

The data in this archive include lineouts and the full time-energy streak. Data are restricted to (0 to 2.8ns) and photon energy (5380 to 5950eV) to match the data regions plotted in Figs. 2 and 3.

Lineouts from Fig. 3 and the raw data are converted to physical units as described in the Supplemental Material. In each, the source emission rate is in units of photons/s/sr/Hz, photon energy is in eV, and time is in nanoseconds.


Funding

This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number(s) DE-NA0004144, and the NSF Physics Frontier Center, Center for Matter at Atomic Pressures (CMAP), under Award PHY-2020249. This work performed under the auspices of the U.S. Department of Energy and an appointment to the Office of Science, by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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