Aims
. This paper presents experimentally obtained rate coefficients for the weakly endothermic reaction OD
−
+ H
2
→ OH
−
+ HD with ortho- and para-hydrogen at astrophysically relevant temperatures ...between 10 and 300 K.
Methods
. The reaction was studied with normal and para-enriched (99.5% para-H
2
) hydrogen in a 22-pole ion trap. The measured temperature dependencies of reaction rate coefficients are analyzed using a model which assumes that the rotational energies of the two reactants are equivalent to the translational energy in driving the reaction.
Results
. At room temperature, the rate coefficients of reactions with both nuclear spin variants reach 7 × 10
−11
cm
3
s
−1
, which is in good agreement with the previous results from ion trap and swarm experiments with normal hydrogen. Cooling down the trap slows down the reaction and leads, at a nominal trap temperature of 11 K, to a rate coefficient below 10
−14
cm
3
s
−1
for para-enriched hydrogen. The fitted reaction endothermicity of 25.3 ± 2.2 meV agrees well with the literature value calculated in the Born-Oppenheimer approximation, Δ
H
0
= 24.0 meV. A simpler evaluation procedure, fitting the data with Arrhenius functions, results in
p
k
= 16.8 × 10
−11
exp(−234 K/
T
) cm
3
s
−1
for pure para-hydrogen and
o
k
= 9.4 × 10
−11
exp(−101 K/
T
) cm
3
s
−1
for pure orthohydrogen.
Rate coefficients for collisional radiative recombination (CRR) of Ar+ ions with electrons were measured in a helium-buffered flowing-afterglow (Cryo-FALP) experiment in temperature range 77-180 K ...and at electron densities ne from 108 to 1010 cm−3. The measured ternary rate coefficient KCRR at 77 K is (1.1 ± 0.4) × 10−17 cm6s−1 and the observed temperature dependence agrees well with the theoretical T−4.5 dependence. A new FALP apparatus operating in the temperature range 40-300 K has been built and the measurements are currently in progress.
Reported are studies of recombination of H3+ ions with electrons in flowing afterglow (FALP) experiment. Reported is observation of dependence of overall recombination process on He pressure and ...hydrogen partial pressure. The obtained data are in good agreement with previous stationary afterglow (AISA) results and clearly indicate the multicollision and multistep character of the recombination process. Proposed is scheme of overall recombination process.
Aims. This paper presents experimentally obtained rate coefficients for the weakly endothermic reaction OD− + H2 → OH− + HD with ortho- and para-hydrogen at astrophysically relevant temperatures ...between 10 and 300 K. Methods. The reaction was studied with normal and para-enriched (99.5% para-H2) hydrogen in a 22-pole ion trap. The measured temperature dependencies of reaction rate coefficients are analyzed using a model which assumes that the rotational energies of the two reactants are equivalent to the translational energy in driving the reaction. Results. At room temperature, the rate coefficients of reactions with both nuclear spin variants reach 7 × 10−11 cm3 s−1, which is in good agreement with the previous results from ion trap and swarm experiments with normal hydrogen. Cooling down the trap slows down the reaction and leads, at a nominal trap temperature of 11 K, to a rate coefficient below 10−14 cm3 s−1 for para-enriched hydrogen. The fitted reaction endothermicity of 25.3 ± 2.2 meV agrees well with the literature value calculated in the Born-Oppenheimer approximation, ΔH0 = 24.0 meV. A simpler evaluation procedure, fitting the data with Arrhenius functions, results in pk = 16.8 × 10−11 exp(−234 K/T) cm3 s−1 for pure para-hydrogen and ok = 9.4 × 10−11 exp(−101 K/T) cm3 s−1 for pure orthohydrogen.
A double chamber vacuum system was constructed for the electron spectroscopy study of GaN layer growth. The samples are prepared by vacuum deposition from Knudsen-type Ga source in the afterglow ...atmosphere of active nitrogen produced by high-pressure RF-plasma source. The growth chamber is connected to the analysis chamber equipped with electron spectroscopy (XPS, AES) analysis, permitting to study the chemical composition of layers as a function of growing conditions. It is shown that the new RF-source is suitable for preparation of pure stoichiometric GaN layers.
collision systems (, HD, D, ≤5), it is emphasized that although the required potential energy surfaces are well characterized, no detailed treatments
of the collision dynamics are available to date, ...especially at the low energies required for astrochemistry. Instead of treating
state-to-state dynamics with state of the art methods, predictions are still based on: (i) simple thermodynamical arguments,
(ii) crude reaction models such as H atom exchange or proton jump, or (iii) statistical considerations used for describing
processes proceeding via long-lived or strongly interacting collision complexes. A central problem is to properly account
for the consequences of the fact that H and D are fermions and bosons, respectively., in a trap, an, In the experimental and results sections, it is emphasized that although a variety of innovative techniques are available
and have been used for measuring rate coefficients, cross-sections or state-to-state transition probabilities, the definitive
experiments are still pending. In the centre of this contribution are our activities on various, =5 systems. We report a few selected additional results for collisions of hydrogen ions with, or well-defined mixtures of these neutrals. Most of the recent experiments are based on temperature variable multipole ion
traps and their combination with pulsed gas inlets, molecular beams, laser probing or electron beams. Based on the state-specific
model calculations, it is concluded that for completely understanding the gas phase formation and destruction of, in situ, This contribution summarizes a variety of results and ongoing activities, which contribute to our understanding of inelastic
and reactive collisions involving hydrogen ions. In an overview of our present theoretical knowledge of various, characterization of all the experimental parameters is required with unprecedented accuracy. Finally, the need to understand
the hydrogen chemistry relevant for dense pre-stellar cores is discussed.
Reported is flowing afterglow (FALP) study of recombination of KrH+ and KrD+ ions with electrons at 250 K in mixtures of He/Kr/H2 and He/Kr/D2, respectively. The influence of fast recombining cluster ...ions formation on apparent effective recombination rate coefficients (αeff) was measured and used in data analysis. The obtained binary rate coefficients for recombination of KrH+ and KrD+ are αKrH+ 2×10−8 cm3s−1 and αKrD+ 1×10−8 cm3s−1.
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