Flowing-afterglow study of electron-ion recombination of para–$H 3 +$ and ortho–$H 3 +$ ions at temperatures from 60 K to 300 K

Detailed measurements employing a combination of a cryogenic flowing afterglow with Langmuir probe (Cryo-FALP II) and a stationary afterglow with near-infrared absorption spectroscopy (SA-CRDS) show that binary electron recombination of $para–H 3 +$ and $ortho–H 3 +$ ions occurs with significantly different rate coefficients, ^pα_bin and ^oα_bin, especially at very low temperatures. The measurements cover temperatures from 60 K to 300 K. At the lowest temperature of 60 K, recombination of $para–H 3 +$ is at least three times faster than that of $ortho–H 3 +$ $( p α bin = ( 1 . 8 ± 0 . 4 ) × 1 0 − 7 cm 3 s − 1 vs . o α bin = ( 0 − 0 + 5 ) × 1 0 − 8 cm 3 s − 1 )$⁠.