Observation of finite-wavelength screening in high-energy-density matter

Abstract

A key component for the description of charged particle systems is the screening of the Coulomb interaction between charge carriers. First investigated in the 1920s by Debye and Hückel for electrolytes, charge screening is important for determining the structural and transport properties of matter as diverse as astrophysical and laboratory plasmas, nuclear matter such as quark-gluon plasmas, electrons in solids, planetary cores and charged macromolecules. For systems with negligible dynamics, screening is still mostly described using a Debye–Hückel-type approach. Here, we report the novel observation of a significant departure from the Debye–Hückel-type model in high-energy-density matter by probing laser-driven, shock-compressed plastic with high-energy X-rays. We use spectrally resolved X-ray scattering in a geometry that enables direct investigation of the screening cloud, and demonstrate that the observed elastic scattering amplitude is only well described within a more general approach.

Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds

“…It is accepted that experimental techniques that provide reliable charge transport measurements, on a single-molecule level, are based on various types of break junctions 1–4. Their strength lies in providing measurement protocols5–9 based on extensive data analysis5 and they allow the study of structure–conductivity relationships in a large variety of molecular systems with different functionalities,5–9 which include rectifiers, diodes, switches and transistors, and functionalities based on physical phenomena with no classical analogue, such as quantum interference effects 10–12…”

Characterizing plasma conditions in radiatively heated solid-density samples with x-ray Thomson scattering

“…where ω is the energy transferred from the electron by Compton scattering, f (k) is the ionic form factor, q(k) is the electronic screening cloud contribution, S ii is the ion density correlation function, Z f is the ionization state, S ee is the free-free dynamic structure factor, Z b is the bound charge per atom, S be is the form factor of bound electrons undergoing Raman-like transitions to the continuum, which is modulated by the self-motion of the FIG. 4. a) The boron ion structure factor versus k for solid density (2.36 g cm −3 ), 10 eV boron with ZB = 3.0, as calculated by several models available in the MCSS code [40,41]: Debye-Hückel [42], Effective-Coulomb, and finite-wavelength screening [34]. b) A plot of the B screening cloud contribution versus k as calculated by several models available for the electron-ion potential in the MCSS code [40,41]: Effective-Coulomb, the Hard Empty Core, and the Soft Empty Core.…”

“…More recent work in XRTS focuses on the information found in the elastic scattering feature; various authors use the strength of the elastic scattering feature to deduce plasma properties, such as the ion structure factor [32], the ionization state [4,5,30,36,49,50], or the screening properties [34]. The values of f (k), q(k), and S ii (k, ω) all depend on the magnitude of the scattering vector, k, which depends on the frequency of incident radiation, ω i , and the scattering angle, θ.…”

“…In addition, the interpretation of XRTS spectra from the non-uniform, inhomogeneous plasmas formed in complex experimental geometries relies on accurate modeling of how x-rays scatter from plasma electrons [30,31]. This includes modeling of atomic form factors, structure factors [32,33], screening contributions [34], and the physics of the electrons that undergo Raman-like transitions to the continuum [4]. There has been limited experimental data available from uniform conditions to validate the many models used in interpreting XRTS data.…”

Unified Concept of Effective One Component Plasma for Hot Dense Plasmas

“…In practice, the Yukawa model is deeply modified in the interpretation of x-ray Thomson scattering experiments by the introduction of short-range hard-core corrections that extends further than the first neighbors range [12, 13]. All these simplifying assumptions can obscure the diagnostic of the phenomena at play as is revealed by more realistic models [14][15][16] and recent experiments [17].These approaches are not satisfactory for actual plasmas because ionization is not a well-defined quantity and the screening length definition is somewhat arbitrary. To provide a more realistic modeling of hot and dense plasmas, we have developed a simple finite temperature Thomas-Fermi orbital-free formulation coupled with molecular dynamics (OFMD) [7].…”