Ternary Association Reaction of Vibrationally Cold N Ions in Ambient Helium.

The rate coefficients for the ternary association reaction of vibrationally cold N ions with N and He were measured in an afterglow plasma in the temperature range of 140-250 K: = (1.02 ± 0.39)(300/) × 10 cm s.

Dissociative recombination of NH ions with electrons in the temperature range of 80-350 K.

Recombination of NH ions with electrons was studied using a stationary afterglow with a cavity ring-down spectrometer. We probed in situ the time evolutions of number densities of different rotational and vibrational states of recombining NH ions and determined the thermal recombination rate coefficients for NH in the temperature range of 80-350 K. The newly calculated vibrational transition moments of NH are used to explain the different values of recombination rate coefficients obtained in some of the previous studies.

Towards state selective recombination of H under astrophysically relevant conditions.

We present studies on the thermalisation of H3+ ions in a cold He/Ar/H2 plasma at temperatures 30-70 K. We show that we are able to generate a rotationally thermalised H3+ ensemble with a population of rotational and nuclear spin states corresponding to a particular ion translational temperature. By varying the para-H2 fraction used in the experiment we are able to produce para-H3+ ions with fractional populations higher than those corresponding to thermodynamic values.

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

The recombination of deuterated trihydrogen cations with electrons has been studied in afterglow plasmas containing mixtures of helium, argon, hydrogen and deuterium. By monitoring the fractional abundances of H3(+), H2D(+), HD2(+) and D3(+) as a function of the [D2]/[H2] ratio using infrared absorption observed in a cavity ring down absorption spectrometer (CRDS), it was possible to deduce effective recombination rate coefficients for H2D(+) and HD2(+) ions at a temperature of 80 K. From pressure dependences of the measured effective recombination rate coefficients the binary and the ternary recombination rate coefficients for both ions have been determined.

Electron Transfer and Associative Detachment in Low-Temperature Collisions of D(-) with H.

The interaction of D(-) with H was studied experimentally and theoretically at low temperatures. The rate coefficients of associative detachment and electron transfer reactions were measured in the temperature range 10-160 K using a combination of a cryogenic 22-pole trap with a cold effusive beam of atomic hydrogen. Results from quantum-mechanical calculations are in good agreement with the experimental data.

Flowing-afterglow study of electron-ion recombination of para-H3(+) and ortho-H3(+) 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-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.

H/D exchange in reactions of OH(-) with D2 and of OD(-) with H2 at low temperatures.

Using a cryogenic linear 22-pole rf ion trap, rate coefficients for H/D exchange reactions of OH(-) with D2 (1) and OD(-) with H2 (2) have been measured at temperatures between 11 K and 300 K with normal hydrogen. Below 60 K, we obtained k1 = 5.5 × 10(-10) cm(3) s(-1) for the exoergic .

Binary recombination of H3(+) and D3(+) ions with electrons in plasma at 50-230 K.

The results of an experimental study of the H3(+) and D3(+) ions recombination with electrons in afterglow plasmas in the temperature range 50-230 K are presented. A flowing afterglow apparatus equipped with a Langmuir probe was used to measure the evolution of the electron number density in the decaying plasma. The obtained values of the binary recombination rate coefficient are αbinH3(+) = (6.

Binary and ternary recombination of D3+ ions at 80-130 K: application of laser absorption spectroscopy.

Recombination of D(3)(+) ions with electrons at low temperatures (80-130 K) was studied using spectroscopic determination of D(3)(+) 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.

Stabilization of H+-H2 collision complexes between 11 and 28 K.

Formation of H(3)(+) via association of H(+) with H(2) has been studied at low temperatures using a 22-pole radiofrequency trap. Operating at hydrogen number densities from 10(11) to 10(14) cm(-3), the contributions of radiative, k(r), and ternary, k(3), association have been extracted from the measured apparent binary rate coefficients, k*=k(r)+k(3)[H(2)]. Surprisingly, k(3) is constant between 11 and 22 K, (2.

Binary and ternary recombination of para-H3(+) and ortho-H3(+) with electrons: state selective study at 77-200 K.

Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that H(3)(+) recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states.

Action spectroscopy of H3+ and D2H+ using overtone excitation.

The H3+ ion and its deuterated isotopologues H2D+, D2H+ and D3+ play an important role in astrophysical and laboratory plasmas. The main challenge for understanding these ions and their interaction at low temperatures are state-specific experiments. This requires manipulation and a simple but efficient in situ characterization of their low-lying rotational states.