The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochro...The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work.Time evolutions of the photoionization properties of the four-color,three-step process are given.The population trapping effects occur intensely in monochromatic excitation,while it gradually turns weak as the laser bandwidth increases.The effects of bandwidth,Rabi frequency,time delay,and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields.The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed.The ionization probability and selectivity factors,as evaluation indexes,are difficult to improve synchronously by adjusting systematic parameters.Besides,the existence of metastable state may play a negative role when its population is low enough.展开更多
The Eq.(6)about the time correlation function of the chaotic field model is corrected,along with the corresponding statement.The enlargement factors of ρ_(33,B) and ρ_(ion,B) in the legends of Figs.2(b),2(c)and 2(d)...The Eq.(6)about the time correlation function of the chaotic field model is corrected,along with the corresponding statement.The enlargement factors of ρ_(33,B) and ρ_(ion,B) in the legends of Figs.2(b),2(c)and 2(d)are corrected.These corrections do not affect the conclusions of the work[Chin.Phys.B 31063203(2022)].展开更多
The atomic selective multi-step photoionization process is a critical step in laser isotope separation.In this work,we study three-step photoionization processes with non-monochromatic laser fields theoretically based...The atomic selective multi-step photoionization process is a critical step in laser isotope separation.In this work,we study three-step photoionization processes with non-monochromatic laser fields theoretically based on the semi-classical theory.Firstly,three bandwidth models,including the chaotic field model,de-correlation model,and phase diffusion model,are introduced into the density matrix equations.The numerical results are compared with each other comprehensively.The phase diffusion model is selected for further simulations in terms of the correspondence degree to physical practice.Subsequently,numerical calculations are carried out to identify the influences of systematic parameters,including laser parameters(Rabi frequency,bandwidth,relative time delay,frequency detuning)and atomic Doppler broadening,on photoionization processes.In order to determine the optimal match among different systematic parameters,the ionization yield of resonant isotope,and selectivity factor are adopted as evaluation indexes to guide the design and optimization process.The results in this work can provide a rewarding reference for laser isotope separation.展开更多
The processes of electric ion extraction from plasma induced by pulse lasers are simulated by particle-in-cell(PIC)method and hybrid-PIC method.A new calculation scheme named preprocessing hybrid-PIC is presented beca...The processes of electric ion extraction from plasma induced by pulse lasers are simulated by particle-in-cell(PIC)method and hybrid-PIC method.A new calculation scheme named preprocessing hybrid-PIC is presented because neither of the two methods above is omnipotent,especially under the circumstance of high initial plasma density.The new scheme provides credible results with less computational consumption than PIC method in both one-and two-dimensional simulations,except forΠ-type electrode configuration.The simulation results show that the M-type performs best in all electrode configurations in both high-density and low-density plasma conditions.展开更多
Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98...Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98 cm^(-1))→auto-ionization state(52353 cm^(-1))→Yb^(+),by the density matrix theory with the consideration of atomic hyperfine structures and magnetic sublevels.To examine the physical model,the numerical isotopic abundance of ytterbium is compared with that from mass spectroscopy experiment,showing that they are in good agreement with each other.The excitation process and ionization process of ytterbium,especially for odd isotopes,are discussed and analyzed in detail on this basis.The effects of frequency detuning,power densities,spectral bandwidths,polarization of two excitation lasers,and atomic Doppler broadening on the total ionization yield and isotopic abundance are investigated numerically and the optimal excitation conditions for~(176)Yb enrichment are identified semi-quantitatively.展开更多
文摘The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work.Time evolutions of the photoionization properties of the four-color,three-step process are given.The population trapping effects occur intensely in monochromatic excitation,while it gradually turns weak as the laser bandwidth increases.The effects of bandwidth,Rabi frequency,time delay,and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields.The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed.The ionization probability and selectivity factors,as evaluation indexes,are difficult to improve synchronously by adjusting systematic parameters.Besides,the existence of metastable state may play a negative role when its population is low enough.
文摘The Eq.(6)about the time correlation function of the chaotic field model is corrected,along with the corresponding statement.The enlargement factors of ρ_(33,B) and ρ_(ion,B) in the legends of Figs.2(b),2(c)and 2(d)are corrected.These corrections do not affect the conclusions of the work[Chin.Phys.B 31063203(2022)].
文摘The atomic selective multi-step photoionization process is a critical step in laser isotope separation.In this work,we study three-step photoionization processes with non-monochromatic laser fields theoretically based on the semi-classical theory.Firstly,three bandwidth models,including the chaotic field model,de-correlation model,and phase diffusion model,are introduced into the density matrix equations.The numerical results are compared with each other comprehensively.The phase diffusion model is selected for further simulations in terms of the correspondence degree to physical practice.Subsequently,numerical calculations are carried out to identify the influences of systematic parameters,including laser parameters(Rabi frequency,bandwidth,relative time delay,frequency detuning)and atomic Doppler broadening,on photoionization processes.In order to determine the optimal match among different systematic parameters,the ionization yield of resonant isotope,and selectivity factor are adopted as evaluation indexes to guide the design and optimization process.The results in this work can provide a rewarding reference for laser isotope separation.
文摘The processes of electric ion extraction from plasma induced by pulse lasers are simulated by particle-in-cell(PIC)method and hybrid-PIC method.A new calculation scheme named preprocessing hybrid-PIC is presented because neither of the two methods above is omnipotent,especially under the circumstance of high initial plasma density.The new scheme provides credible results with less computational consumption than PIC method in both one-and two-dimensional simulations,except forΠ-type electrode configuration.The simulation results show that the M-type performs best in all electrode configurations in both high-density and low-density plasma conditions.
文摘Selective photoionization of ytterbium isotope is studied numerically based on a three-step photoionization scheme,4f^(14)6s^(21)S_0(0 cm^(-1))→4f~(14)6s6p~3P_1(17992.008 cm^(-1))→(4f~(13)6s~26p)(7/2,3/2)_2(35196.98 cm^(-1))→auto-ionization state(52353 cm^(-1))→Yb^(+),by the density matrix theory with the consideration of atomic hyperfine structures and magnetic sublevels.To examine the physical model,the numerical isotopic abundance of ytterbium is compared with that from mass spectroscopy experiment,showing that they are in good agreement with each other.The excitation process and ionization process of ytterbium,especially for odd isotopes,are discussed and analyzed in detail on this basis.The effects of frequency detuning,power densities,spectral bandwidths,polarization of two excitation lasers,and atomic Doppler broadening on the total ionization yield and isotopic abundance are investigated numerically and the optimal excitation conditions for~(176)Yb enrichment are identified semi-quantitatively.
