| The study of the transition rate in hot dense plasma is of great significance.In theory,a detailed study of the transition rate can combine atomic physics with statistical physics and explore the laws of physics in complex systems.In practice,the transition rate will directly determine the charge state distribution of the plasma,and then affect the plasma’s state equation,radiative opacity,and the evolution characteristics of non-equilibrium plasma.Therefore,studying the transition rate in hot dense plasma is very important for basic science,the establishment of celestial models,and the practical application of high energy density physics.The transition rate reflects the speed of atomic state transition in the system,and is closely related to the inelastic collision process between electrons and atoms,especially the cross section of the electron-impact ionization process.Researching hot dense plasma is difficult due to its ion-ion coupling and electron-electron degeneracy.In previous work,Jin Yang et al.of the National University of Defense Technology obtained part of the atomic structure of the atom through the electronelectron and ion-ion correlation functions under the hypernetted-chain(HNC)approximation.On this basis,this paper firstly uses the Flexible-Atomic-Code(FAC)to study the movement of atomic energy levels under the electron-electron and ion-ion correlation effects in hot dense plasma,and calculate ionization potential depression(IPD)through two-step Hartree-Fock-Slater model.The electron-impact ionization cross section is calculated by the transition matrix element,which will be influenced by the change of the continuous electron wave function.In hot dense plasma environment,due to the interaction of scattered electrons with surrounding free electrons and ions during the collision,the scattered electrons have a momentum relaxation effect,which result in the damping of wave function of scattered electrons when moving away from the target atom,and the decay factor is obtained by Born-Mermin approximation(BMA).This paper considers the dynamic correlation between plasma and scattered electrons from a phenomenological point of view,so as to study the electron-impact ionization process.Based on the above considerations,in Mg7+plasma with an electron temperature of 75 eV and a free electron density of 3×1023 cm-3,we calculate the electron-impact ionization cross section of e+1s2s22p2 2P1/2-1s2s22p+2e of Mg7+,we find the IPD and damping of scattered electron increases the electron-impact ionization cross section by nearly an order of magnitude,which is in good agreement with the experimental results of Berg et al.Considering the distribution of different charge states in the plasma,the influence of the distribution of different charge states in the Al plasma on the IPD was studied.We use the Saha equation to give the ion charge state fraction as a weighting factor under the local thermal dynamic equilibrium approximation,and perform a weighted average of the correlation functions between different charge state to obtain the average correlation function.It is found that for a wider distribution of charge states,the difference between the results under the one-component plasma and the average correlation function is greater.Different from IPD at a fixed density and different temperatures,the change of density has a great influence on IPD.For the temperature of 100 eV,when Z=5,6,and 7,the results of 3.6g/cm3 are in excellent agreement with experimental results and other models,When Z increases to Z=8 and 9,there is a good agreement between the results of 5.4 g/cm3 and the experiment.The mentioned above studys the electron-atom collision process by the influences of the atomic structure of in plasma environment,and phenomenologically considering the dynamic relationship between the plasma and scattered electrons.In order to theoretically rigorously discuss the influence of the plasma environment on the atomic transition rate.This paper starting from the correlation of plasma density fluctuations,think that the fluctuations in the Coulomb potential field caused by the density fluctuations of charged particles will make an important contribution to the atomic transition process.From this,the theoretical formula of the transition rate is further deduced,which takes into account the plasma dynamic correlation and collective excitation effect.Take the 1s-2s excitation transition of the hydrogen atom as an example.Under the decoupling approximation,the results are different from the results under the traditional Maxwell distribution.The present results are more concentrated and located in the middle of the Maxwell distribution results,and are much less affected by changes in the number of particles.At a lower temperature between 10 eV and 50 eV,increasing the density don’t contribute much to the transition rate of hydrogen atoms.Although the electron density has increased by an order of magnitude,the difference in the corresponding dynamic structure factor has become larger,making up for the difference caused by the density change.When the temperature of the system increases,the difference between the dynamic structure factors becomes smaller,so that the increase in density makes a greater contribution to the transition rate. |
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