Flowing-afterglow study of electron-ion recombination of para–H3+ and ortho–H3+ ions at temperatures from 60 K to 300 K

Abstract

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-H3(+) and ortho-H3(+) ions occurs with significantly different rate coefficients, (p)αbin and (o)αbin, 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-H3(+) is at least three times faster than that of ortho-H3(+) ((p)αbin=(1.8±0.4)×10(-7) cm(3) s(-1) vs. (o)αbin=(0-0 (+5))×10(-8) cm(3) s(-1)).

Binary and ternary recombination of H2D+ and HD2+ ions with electrons at 80 K

“…In our previous studies we monitored the approach to equilibrium of afterglow plasmas in He/Ar, He/Ar/H 2 and He/Ar/D 2 gas mixtures. 35,40,41 The kinetic temperature of ions (T kin-ion ) was obtained from Doppler broadening of measured absorption lines. The rotational temperature of ions (T rot ) was determined by measuring relative populations of the lowest rotational states.…”

“…The rotational temperature of ions (T rot ) was determined by measuring relative populations of the lowest rotational states. 41 The electron temperature (T e ) was estimated by monitoring the losses due to the ambipolar diffusion. 29,41,42 Because excited particles can heat the electrons in superelastic collisions, we also monitored the presence of the ground and the first vibrational state of the a 3 S + u electronic state of (He 2 )* and the 3s 2 3p 5 ( 2 P 0 1/2 )3d 2 [3/2] 0 state of (Ar)* during the afterglow.…”

Rydberg States of H3 and HeH as Potential Coolants for Primordial Star Formation

“…Para-H 3 + DR rates increase, while ortho-H 3 + rates decrease. As such, the dissociative recombination patterns were experimentally determined below 100 K. Later, in 2015, it would be found that the 60 K binary recombination rate for para-H 3 + (1.8 × 10 –7 cm 3 s –1 ) is at least three times larger than for ortho-H 3 + (0 +5 × 10 –8 cm 3 s –1 ) …”

“…As such, the dissociative recombination patterns were experimentally determined below 100 K. Later, in 2015, it would be found that the 60 K binary recombination rate for para-H 3 + (1.8 × 10 −7 cm 3 s −1 ) is at least three times larger than for ortho-H 3 + (0 +5 × 10 −8 cm 3 s −1 ). 43 In 2013, studies extended conditions down to 50 K for the first time for both H 3 + and D 3 + DR. Differing from neutral ternary recombination (He assisted), electron-assisted ternary recombination (electron-collisional radiative recombination or E-CRR) may also substantially contribute to effective recombination rates, which was suggested by theory and observed in an Ar + dominated plasma.…”

Reaction of NH+, NH2+, and NH3+ ions with H2 at low temperatures

“…In normal H 2 , the para/ortho ratio is 1/3, corresponding to the thermal equilibrium at 300 K (for discussion, see Zymak et al 2013;Hejduk et al 2012). As the rotational excitation in hydrogen gas is thermalized only within para and ortho manifolds, H 2 gas flowing through the gas inlet system into the trap volume is not thermalized at trap temperatures below 200 K (Zymak et al 2013;Hejduk et al 2015). The gas number density inside the ion trap is determined using a spinning rotor gauge and a calibrated ionization gauge with estimated uncertainty of 20%.…”