Effect Of Dielectronic Recombination On Charge-state Distribution In Laser-produced Plasma

There are complex ionization and recombination processes in laser-produced plasma from generation to expanding and cooling.The interaction between these atomic processes determines the state of the plasma,which makes the plasma have a complex spectral structure and a strong spatial gradient of electron temperature and density.The dielectronic recombination?DR?process plays an important role in determining the ionization equilibrium and charge-state distribution of the plasma.In this paper,the effect of DR on the charge-state distribution in laser-produced plasma has been studied,and the influence of DR process on the radiation characteristics and dynamic evolution behavior of plasma were also revealed.It is expected to provide an important reference for the research of astrophysics,soft X-ray source,controlled fusion.In this paper,based on the collisional-radiative?CR?model proposed by colombant and Tonon,three different types of CR models including DR process were constructed.Taking laser-produced Si plasma as a research object,the effects of DR process on the electronic temperature,electronic density and charge-state distribution of laser-produced Si plasma were indicated by the comparison and analysis of these models.The specific work includes the following two aspects:?1?Three main factors of influencing the DR rate coefficient that the dependence of partial DR rate coefficients on the radiative transition final state,the dependence of partial DR rate coefficients on orbital angular momentum l',the dependence of partial DR rate coefficients on primary quantum number n',were detailedly analyzed.Ab initio calculations of DR rate coefficients of Si⁴⁺-Si⁶⁺ions have been performed by using FAC?Flexible atomic code?package and compared with those in ADAS?Atomic data and analysis system?database.?2?The extreme ultraviolet emission spectra of Si ions from laser-produced plasma have been obtained at different delay times by using a high-precision spatio-temporally resolved spectroscopy setup.These experimental spectra were identified by using the experimental spectral line with the spectral line information of Si atom of NIST?National institute of standards and technology?database.Then,based on the steady-state CR model D including DR process,the experimental spectra have been simulated.The characteristics of the evolution of electron temperature,electron density,rate coefficient of each atomic process and charge-state distribution with delay time were analyzed in detail,and the important influence of DR process on the plasma evolution was indicated.