Plasma Coupling Strength Research Articles

Theoretical studies of dense hydrogen-like plasmas with the unified description of linear screening

A unified framework for describing dense plasma screenings from warm dense matter to hot dense matter, including gradient correction and exchange-correlation, has been recently proposed by Stanton and Murillo [Phys. Rev. E 91,033104 (2015)]. With this unified description of linear screening, the energy levels, absorption oscillator strengths, and radiative transition probabilities of hydrogen-like plasmas are reported for a wide range of critical screening parameters (plasma temperatures and densities), where the bound level nl merges into continuum. The importance of both finite temperature gradient correction and exchange correlation increases with the increasing plasma coupling strength or the Coulomb coupling parameter Γ, and the effect of exchange correlation is generally greater than that of finite temperature gradient correction. Further results from the weakly coupled and strongly coupled limits or Debye plasmas and dense quantum plasmas also show consistency with those from the unified framework, respectively.

Friction force in strongly magnetized plasmas.

A charged particle moving through a plasma experiences a friction force that commonly acts antiparallel to its velocity. It was recently predicted that in strongly magnetized plasmas, in which the plasma particle gyrofrequency exceeds the plasma frequency, the friction also includes a transverse component that is perpendicular to both the velocity and Lorentz force. Here, this prediction is confirmed using molecular-dynamics simulations, and it is shown that the relative magnitude of the transverse component increases with plasma coupling strength. This result influences single-particle motion and macroscopic transport in strongly magnetized plasmas found in a broad range of applications.

Atomic structure under external confinement: effect of plasma on the spin orbit splitting, relativistic mass correction and Darwin term for hydrogen-like ions

The effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analysed systematically for the first time for a range of coupling strengths of the plasma. The Debye plasma environment has been treated under a standard screened Coulomb potential (SCP) while the quantum plasma has been treated under an exponential cosine screened Coulomb potential (ECSCP). Estimation of the spin orbit splitting under SCP and ECSCP plasma is restricted to the lowest two dipole allowed states while for the other two properties, the ground state as well as the first two excited states have been chosen. Calculations have been extended to nuclear charges for which appreciable relativistic corrections are noted. In all cases calculations have been extended up to such screening parameters for which the respective excitation energies tend towards their stability limit determined by the ionisation potential at that screening parameter. Interesting behavior of the respective properties with respect to the plasma coupling strength has been noted.

Hyperpolarizabilities of one and two electron ions under strongly coupled plasma

Systematic investigations on the hyperpolarizabilities of hydrogen and helium like ions up to nuclear charge Z = 7 under strongly coupled plasma environment have been performed. Variation perturbation theory has been adopted to evaluate such properties for the one and two electron systems. For the two electron systems coupled Hartree-Fock theory, which takes care of partial electron correlation effects, has been utilised. Ion sphere model of the strongly coupled plasma, valid for ionic systems only, has been adopted for estimating the effect of plasma environment on the hyperpolarizability. The calculated free ion hyperpolarizability for all the systems is in good agreement with the existing data. Under confinement hyperpolarizabilities of one and two electron ions show interesting trend with respect to plasma coupling strength.

Plasma effects on resonant fusion

I investigate the effects of plasma interactions on resonance-enhanced fusion rates in stars. Starting from basic principles we derive an expression for the fusion rate that can serve as a basis for discussion of approximation schemes The present state-of-the-art correction algorithms, based on the classical correlation function for the fusing particles and the classical energy shift for the resonant state, do not follow from this result, even as an approximation. The results of expanding in a perturbation solution for the case of a weakly coupled plasma are somewhat enlightening. But at this point we are at a loss as to how to do meaningful calculations in systems with even moderate plasma coupling strength. Examples where this can matter are the effect of a possible low-energy ${}^{12}$C+${}^{12}$C resonance on x-ray bursts from accreting neutron stars or on supernova 1A simulations, and the calculation of the triple $\ensuremath{\alpha}$ rate in some of the more strongly coupled regions in which the process enters, such as accretion onto a neutron star.

Hyperpolarizability of two electron atoms under spherically confined Debye plasma

Pilot calculations on the hyperpolarizability of He, the first neutral member of the two electron sequence, have been performed under spherical confinement with a view to analyse the effect of pressure on such non linear optical properties. Detailed investigations have also been performed for the first time on the hyperpolarizability due to the effect of screened Coulomb potential obtained from a surrounding Debye plasma environment. Variation perturbation theory within coupled Hartree-Fock scheme has been adopted to estimate the non linear optical properties under such external confinement. For a given plasma coupling strength, the hyperpolarizability value is found to reduce systematically with decrease of radius of confinement, while the same is found to increase continuously with increasing plasma coupling strength determined by gradual enhancement of the screening parameter for a given radius of confinement. Under strong confinement the hyperpolarizability value is found to be negative. The estimated free atom hyperpolarizability is consistent with the existing coupled Hartree-Fock result.

Formula omitted] and [formula omitted] states of two electron atoms under Debye plasma screening

Extensive non-relativistic variational calculations for estimating the energy values of 2 pnd ( D o 1 , 3 ) states [ n = 3 – 6 ] of two electron atoms (He, Li + , Be 2 + ) and 2 pnp ( P e 1 ) [ n = 3 – 8 ] and 2 pnp ( P e 3 ) states [ n = 2 – 7 ] of Be 2 + under weakly coupled plasma screening have been performed using explicitly correlated Hylleraas type basis. The modified energy eigenvalues of P e 1 , 3 states arising from two p electrons of Be 2 + ion and D o 1 , 3 states due to 2 pnd configuration of Li + and Be 2 + ion in the Debye plasma environment are being reported for the first time. The effect of plasma has been incorporated through the Debye screening model. The system tends towards gradual instability and the number of bound states reduces with increasing plasma coupling strength. The wavelengths for 2 pn ′ p ( P e 1 ) [ n ′ = 3 – 8 ] → 2 pnd ( D o 1 ) [ n = 3 – 6 ] and 2 pn ′ p ( P e 3 ) [ n ′ = 2 – 8 ] → 2 pnd ( D o 3 ) [ n = 3 – 6 ] transitions in plasma embedded two electron atoms have also been reported.

Atomic structure under external confinements: Effect of plasma

AbstractExtensive nonrelativistic studies have been performed on the spectral properties of confined atomic systems under a charge neutral background. The effect of confinement on the spectral properties due to the neutral background has been analyzed using plasma model, which, for weak coupling case, can be obtained from the standard Debye screening model, and for strong coupling case, can be envisaged by ion sphere (IS) model. Further consideration has been given for estimating the effect due to spatially confined plasma, which is obtained by imposing finite boundary conditions on the wave functions. Several atomic, ionic, and exotic systems have been considered for our exclusive study. The structural properties like the ground and excited state energies, oscillator strengths, and transition probabilities for low lying excitations and spectral line shifts have been estimated for hydrogen‐ and helium‐like ions under different plasma coupling strengths. The system approaches towards gradual instability with increase of the plasma coupling strength. A gradual reduction of the ionization potential is observed and the number of bound states become finite. The behavior of ionization potentials, excitation energies, polarizabilities, oscillator strengths, and transition probabilities with respect to increased plasma strength have been found to be interesting. Our findings are in good agreement with limited experimental observations using laser produced plasmas. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

Stability of molecular ion under Debye plasma

Abstract The effect of plasma environment on the binding energy of the Coulomb three body H 2 + molecular ion has been analyzed within nonrelativistic framework. Variational method has been adopted using multi-exponent correlated basis sets involving inter particle coordinates. The effect of external plasma has been incorporated using Debye screening model of the interacting charge particles. The binding energy appears to decrease monotonically towards instability if the plasma coupling strength is gradually increased.

Thermodynamics and structure of liquid metals: a critical assessment of the charged-hard-sphere reference system

The authors calculate the Helmholtz free energies of the liquid alkali metals at various temperatures and those of several polyvalent metals (Mg, Cd, Al, In, Tl and Pb) near freezing, using the variational approach based on the Gibbs-Bogoliubov inequality in conjunction with the charged-hard-sphere reference fluid and with ab initio non-local pseudopotentials for the electron-ion interactions. The reference fluid introduces two variational parameters, i.e. the plasma coupling strength Gamma and the packing fraction eta , and is treated by a thermodynamically self-consistent approach which reduces to a highly accurate description of the one-component classical plasma for eta =0 and of the neutral-hard-sphere fluid for Gamma =0.