Recombination of vibrationally cold N2+ ions with electrons.

Recombination of vibrationally cold N2+ ions with electrons was studied in the temperature range of 140-250 K. A cryogenic stationary afterglow apparatus equipped with cavity ring-down spectrometer and microwave diagnostics was utilized to probe in situ the time evolutions of number densities of particular rotational and vibrational states of N2+ ions and of electrons. The obtained value of the recombination rate coefficient for the recombination of the vibrational ground state of N2+ with electrons is αv=0 = (2.95 ± 0.50) × 10-7(300/T)(0.28±0.07) cm3 s-1, while that for the first vibrationally excited state was inferred as αv=1 = (4 ± 4) × 10-8 cm3 s-1 at 250 K.

Management of ileocolic intussusception in the Czech Republic.

INTRODUCTION: Ileocolic intussusception is one of the most frequent causes of acute abdomen in infants and toddlers. The purpose of this study was to evaluate the treatment of ileocolic intussusception in the Czech Republic in 2019. METHODS: Fourteen departments of paediatric surgery participated in this multicentre retrospective study. A SurveyMonkey Inc. questionnaire was used for anonymous data collection of patients with ileocolic intussusception. RESULTS: In 2019, ileocolic intussusception was diagnosed in 162 patients; median age was 30 months (3 months to 9.5 years). Contrast enema was indicated in 133 patients, primary surgery in 14 patients and spontaneous reduction was found in 15 patients. All departments using contrast enema had a success rate of 89.5%; 12 departments approached the contrast enema procedure under general anaesthesia (including myorelaxation at 7 departments) and 2 departments under sedation. Contrast enema under general anaesthesia with/without myorelaxation was significantly more successful than contrast enema under sedation (108/113, 95.6% vs 11/20, 55%; p.

The reaction of O+(4S) ions with H2, HD, and D2 at low temperatures: Experimental study of the isotope effect.

The reactions of the O+ ions in the 4S electronic ground state with D2 and HD were studied in a cryogenic 22-pole radio-frequency ion trap in the temperature range of 15 K-300 K. The obtained reaction rate coefficients for both reactions are, considering the experimental errors, nearly independent of temperature and close to the values of the corresponding Langevin collisional reaction rate coefficients. The obtained branching ratios for the production of OH+ and OD+ in the reaction of O+(4S) with HD do not change significantly with temperature and are consistent with the results obtained at higher collisional energies by other groups. Particular attention was given to ensure that the O+ ions in the trap are in the ground electronic state.

Stationary afterglow apparatus with CRDS for study of processes in plasmas from 300 K down to 30 K.

A cryogenic stationary afterglow apparatus equipped with a near-infrared cavity-ring-down-spectrometer (Cryo-SA-CRDS) for studies of electron-ion recombination processes in the plasma at temperatures 30-300 K has been designed, constructed, tested, and put into operation. The plasma is generated in a sapphire discharge tube that is contained in a microwave cavity. The cavity and the tube are attached to the second stage of the cold head of the cryocooler system, and they are inserted to an UHV chamber with mirrors for CRDS and vacuum windows on both ends of the tube. The temperature of the discharge tube can be made as low as 25 K. In initial test measurements, the discharge was ignited in He/Ar/H2 or He/H2 gas mixtures and the density of H3+ ions and their kinetic and rotational temperatures were measured during the discharge and afterglow. From the measured decrease in the ion density, during the afterglow, effective recombination rate coefficients were determined. Plasma relaxation was studied in He/Ar gas mixtures by monitoring the presence of highly excited argon atoms. The spectroscopic measurements demonstrated that the kinetic temperature of the ions is equal to the gas temperature and that it can be varied from 300 K down to 30 K.

Ternary recombination of H3(+) and D3(+) with electrons in He-H2 (D2) plasmas at temperatures from 50 to 300 k.

We present results of plasma afterglow experiments on ternary electron-ion recombination rate coefficients of H3(+) and D3(+) ions at temperatures from 50 to 300 K and compare them to possible three-body reaction mechanisms. Resonant electron capture into H3* Rydberg states is likely to be the first step in the ternary recombination, rather than third-body-assisted capture. Subsequent interactions of the Rydberg molecules with ambient neutral and charged particles provide the rate-limiting step that completes the recombination. A semiquantitative model is proposed that reconciles several previously discrepant experimental observations. A rigorous treatment of the problem will require additional theoretical work and experimental investigations.

Binary recombination of para- and ortho-H3+ with electrons at low temperatures.

Results of an experimental study of binary recombination of para- and ortho-H(3)(+) ions with electrons are presented. Near-infrared cavity-ring-down absorption spectroscopy was used to probe the lowest rotational states of H(3)(+) ions in the temperature range of 77-200 K in an H(3)(+)-dominated afterglow plasma. By changing the para/ortho abundance ratio, we were able to obtain the binary recombination rate coefficients for pure and para-H(3)(+) and ortho-H(3)(+). The results are in good agreement with previous theoretical predictions.

Nuclear spin effect on recombination of H3⁺ ions with electrons at 77 K.

Utilizing different ratios of para to ortho H2 in normal and para enriched hydrogen, we varied the population of para-H3⁺ in an H3⁺ dominated plasma at 77 K. Absorption spectroscopy was used to measure the densities of the two lowest rotational states of H3⁺. Monitoring plasma decays at different populations of para-H3⁺ allowed us to determine the rate coefficients for binary recombination of para-H3⁺ and ortho-H3⁺ ions: (p)α(bin)(77 K) = (1.9 ± 0.4) × 10⁻7 cm³ s⁻¹ and (o)α(bin)(77 K) = (0.2 ± 0.2) × 10⁻7 cm³ s⁻¹.

Temperature dependence of binary and ternary recombination of D3+ ions with electrons.

Flowing and stationary afterglow experiments were performed to study the recombination of D(3)(+) ions with electrons at temperatures from 77 to 300 K. A linear dependence of apparent (effective) binary recombination rate coefficients on the pressure of the helium buffer gas was observed. Binary (D(3)(+)+e(-)) and ternary (D(3)(+)+e(-)+He) recombination rate coefficients were derived. The obtained binary rate coefficient agrees with recent theoretical values for dissociative recombination of D(3)(+). We describe the observed ternary process by a mechanism with two rate determining steps. In the first step, a rotationally excited long-lived neutral D(3)* is formed in D(3)(+)-e(-) collisions. As the second step, the D(3)* collides with a helium atom that prevents autoionization of D(3)*. We calculate lifetimes of D(3)* formed from ortho-, para-, or metastates of D(3)(+) and use the lifetimes to calculate ternary recombination rate coefficients.