Theoretical Study On Resonant Electronic Recombination And Radiation Spectrum Polarization Property Of B-like Isoelectronic Sequence Ions

The resonant electronic recombination is a basic atomic process,in which a free electron is captured by a highly charged target ion to form a resonant intermediate（autoionization）state of the recombined ion,and then emits photons by radiative transition process.It is an important dynamic process that affects the ionization balance and spectral characteristics in high-temperature plasma.The satellite line spectrum emitted by this process provides an important tool for diagnosis of plasma temperature and density.High-precision physical parameters,such as cross sections and rate coefficients,are particularly important for simulating and diagnosing various plasmas.In recent years,with the improvement of the experimental equipment such as heavy-ion storage ring and electron beam ion trap（EBIT）,people can obtained so high-precision resonant electronic recombination spectra experimentally of some highly charged ions,that the contribution of some high-order processes can be distinguished.Based on the relativistic configuration interaction theory,resonant electronic recombination process and polarization properties of radiative transition photons of highly charged silicon ions(Si⁹⁺)and boron-like isoelectronic sequence ions have been studied systematically by using the Flexible Atomic Code（FAC）program.It mainly includes the following two aspects:Firstly,the resonant electronic recombination process and polarization properties of emitted photons are studied for boron-like silicon ions in the ground state(1s²2s²2p_1/2)and metastable state(1s²2s²2p_3/2),respectively.In the calculation,the resonant intermediate state includes all possible K-shell resonance states of Si⁹⁺ion,and the radiation final state includes 1s²2s²2p²,1s²2s2p³ and 1s²2p⁴ states.The resonance energy,resonance strength produced by dielectronic recombination（DR）,trielectronic recombination（TR）,and quadruelectronic recombination（QR）channels are studied in detail.The calculation results are compared with the available theoretical results,and good agreement is found.A comparison is made for resonance peaks and cross sections between the ground state and metastable state,it is found that are on the same order of magnitude.The resonance peaks are mainly distributed within the range of1430-1456eV of the resonance energy.The resonance strength of TR process occupies a large proportion in resonant electronic recombination process,indicating that it cannot be ignored.The orientation parameters A₂,anisotropy parametersα₂^df,and the degree of linear polarization are calculated for several significant transition satellite lines.It is found that for the lines such as[1s2s²2p_1/22p²]₁→[1s²2s²2p²_1/2]₀,they have larger degree of linear polarization,which is easily observed.We hope the present theoretical results of resonance strength and linear polarizations are useful for identifying spectrum,diagnosing temperature and density precisely of astrophysics in the future.Secondly,the K-shell resonant electronic recombination process and corresponding polarization properties of the radiation spectrum are studied for boron-like isoelectronic sequence（Z=10-54）ions in the ground state.The energy level,radiative transition rate and Auger rate for all resonant states formed by DR,TR and QR processes are systematically calculated,as well as the degree of polarization for radiation spectrum.We compared the resonance energy and resonance strength with the latest international EBIT measurements for Ar¹³⁺,Fe²¹⁺,Kr³¹⁺,I⁴⁸⁺and Xe⁴⁹⁺ions,which shows good agreement.On this basis,the contributions of DR,TR and QR processes to total strength are explored for B-like isoelectronic ions depending on the atomic number Z,it is found that the TR process is very significant for low Z system.There are strong configuration mixing between[1s2s²2p³_3/2]₂（from TR）and[1s2s²2p_1/22p²_3/2]₂（from QR）which resulting in an irregular change of TR/DR ratio near Z=23.It also strongly affect the degree of polarization for radiative transition photons.This is the first systematic study of the degree of polarization of radiative photons for boron-like ions.