Binary and ternary recombination ofD3+ions with electrons inHe-D2plasma

Abstract

An experimental study is reported about the recombination of $\text{D}_{3}{}^{+}$ ions with electrons in a low-temperature plasma (200--300 K) consisting of He with a small admixture of ${\text{D}}_{2}$. At several temperatures, the pressure dependence of the apparent binary recombination rate coefficient $({\ensuremath{\alpha}}_{\text{eff}})$ was measured over a broad range of helium pressures (200--2000 Pa). The binary and ternary recombination rate coefficients were obtained from measured pressure dependences of ${\ensuremath{\alpha}}_{\text{eff}}$. The binary recombination rate coefficient obtained ${\ensuremath{\alpha}}_{\text{bin}}(300\text{ }\text{K})=(2.7\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }{\text{cm}}^{3}\text{ }{\text{s}}^{\ensuremath{-}1}$ is in agreement with recent theory. The ternary recombination rate coefficient obtained is ${K}_{\text{He}}(300\text{ }\text{K})=(1.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}\text{ }{\text{cm}}^{6}\text{ }{\text{s}}^{\ensuremath{-}1}$. In analogy with the recently described process of helium-assisted ternary recombination of $\text{H}_{3}{}^{+}$ ions, it is suggested that the ternary helium-assisted recombination of $\text{D}_{3}{}^{+}$ ions proceeds through the formation of a neutral long-lived highly excited Rydberg molecule ${\text{D}}_{3}$ followed by a collision with a He atom.