Binary and ternary recombination of ${\rm D}_3 registered $D3+ ions at 80--130 K: Application of laser absorption spectroscopy

Recombination of ${\rm D}_3 registered $D3+ ions with electrons at low temperatures (80-130 K) was studied using spectroscopic determination of ${\rm D}_3 registered $D3+ ions density in afterglow plasmas. The use of cavity ring-down absorption spectroscopy enabled an in situ determination of the abundances of the ions in plasma and the translational and the rotational temperatures of the recombining ions. Two near infrared transitions at (5792.70 plus or minus 0.01) cm-1 and at (5793.90 plus or minus 0.01) cm-1 were used to probe the number densities of the lowest ortho state and of one higher lying rotational state of the vibrational ground state of ${\rm D}_3 registered $D3+ ion. The results show that ${\rm D}_3 registered $D3+ recombination with electrons consists of the binary and the third-body (helium) assisted process. The obtained binary recombination rate coefficients are in agreement with a recent theoretical prediction for electron-ion plasma in thermodynamic equilibrium with alpha bin(80 K) = (9.2 plus or minus 2.0) 10-8 cm3 s-1. The measured helium assisted ternary rate coefficients KHe are in agreement with our previously measured flowing afterglow data giving a value of KHe(80 K) = (1.2 plus or minus 0.3) 10-25 cm6 s-1.