Slowdown of the recombination of ultracold xenon plasma created by two -step photoionization of Xe-atoms

Abstract This paper discusses the results of a numerical study of the two-step photoionization kinetics of xenon atoms and plasma recombination. At initial electron temperatures <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≥</mml:mo> <mml:mn>0.5</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">K</mml:mi> </mml:math> during the pump laser ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>882</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">nm</mml:mi> </mml:math> ) and the ionizing laser ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>514</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">nm</mml:mi> </mml:math> ) action, the electrons are heated in superelastic collisions and in three-body recombination. As a result, the electron temperature increases by almost two order of magnitude. This causes the plasma recombination to slowdown, which fits well into the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> dependence of the three-body recombination coefficient. At times <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>t</mml:mi> <mml:mo>≥</mml:mo> <mml:mn>1</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> </mml:math> , the electron temperature decreases due to the adiabatic expansion of the plasma droplet. The method of resonance fluorescence of the atomic line ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>882</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">nm</mml:mi> </mml:math> ) allows extracting the temperature dependence of electrons on time.