Thermal electron attachment processes in gas mixtures containing H2S, HCl and HBr

Szamrej, I.; Janicka, H.; Chrząścik, Ireneusz; Foryś, M.

doi:10.1016/1359-0197(89)90037-4

Cited by 2 publications

(2 citation statements)

References 26 publications

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“…: In these early studies the rate of reaction 3 was followed by competing the HBr against the specific electron scavenger SF 6 . More recently the second order dependence on HBr was confirmed by totally independent physical experiments, which employed the thermal electron swarm method . As well as the dependence on HBr concentration, the rate constants observed were in agreement with those obtained by the competition method.…”

Section: Introductionsupporting

confidence: 77%

Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study

Rauk

2000

J. Phys. Chem. A

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Experimental studies have shown that the dissociative attachment of electrons to HBr monomer; viz., HBr + e- → H• + Br- is an endothermic process, which requires electrons of energy near the endothermicity (ΔE = +38 kJ/mol). In contrast the attachment to the dimer via the reaction: HBr·HBr + e- ⇌ HBr·HBr•- → H• + BrHBr- proceeds readily with electrons of thermal (i.e., near zero) energy. The energetics of the reactions with both the monomer and the dimer have been studied by ab initio methods. In each case the structure of the neutral and anion species have been computed using large basis sets and diffuse orbitals at the MP2 level. Energies have been obtained at this level and at the CCSD(T) level. The initial interaction of the free electron with the molecule produces a dipole continuum state (DCS) of the anion. The DCS subsequently undergoes a transition to a bound state via an avoided crossing. On the basis of the CCSD(T) energies, the H−Br • -···HBr interaction lowers the energy for dissociation of the H−Br • - bond to the thermal energy range. Also the decomposition of HBr·HBr • - to H • and BrHBr- is 47 kJ/mol exergonic and the BrHBr- fragment is expected to be in a vibrationally excited state. In both the monomer and dimer anions the transition from DCS to the bound valence state is very sudden, and is marked by enormous (10-fold) changes in the dimensions of the orbitals occupied by the electron.

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Section: Introductionsupporting

confidence: 77%

Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study

Rauk

2000

J. Phys. Chem. A

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“…However, in the case of HBr it is exothermic. Also both chemical experiments 16 and electron swarm studies 17 have shown that at thermal energies dissociative capture by the neutral dimer is fast. Recent ab initio calculations 18 have confirmed that the potential energy barrier for this process is negligible, and the BrHBrcarries excess vibrational energy.…”

Section: Introductionmentioning

confidence: 99%

An ab Initio Study of Linear XH−HX Hydrogen Halide Anions

Rauk

2001

J. Phys. Chem. A

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This paper examines the stabilities of singly charged anions with the linear opposed dipole structures: FH-HF, ClH-HCl and BrH-HBr at MP2 and CCSD(T) levels. With 6-311+G(3df,2p) basis sets on Cl and Br and aug-cc-pvdz on H and F, MP2 structures were obtained for all three systems. Since the neutral dimers with opposed dipoles are unstable, the energies for the electron detachment processes were evaluated relative to separated free neutrals, viz.: XH-HX‚f e -+ 2HX. At the CCSD(T) level these energies were 0.26 and 0.84 V for HCl and HBr, respectively, but the value for HF is negative. The addition of diffuse orbitals at the central point between the two H atoms lowered the energy and caused the H-H distance in the FH-HF species to increase. Also the excess electron moved into the diffuse orbitals and the species assumed a solvated electron structure, a finding which is in agreement with previous work. In contrast, for the HCl and HBr species the addition of diffuse orbitals had no significant effect. The optimized geometries, charge and spin distributions, and the adiabatic electron detachment energies all remained essentially unchanged. This result and other molecular parameters indicated that in the ClH-HCl and BrH-HBr anions the extra electrons were located in valence orbitals made up from the σ* orbitals of the two HX molecules. The nature of these orbitals was discussed. Since the dipole moment of the HCl.HCl neutral dimer is considered too small for formation of a dipole-bound anion state (as occurs with HF.HF), it is quite probable that HCl dimer anion observed experimentally is of the XH-HX‚type.

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Thermal electron attachment processes in gas mixtures containing H2S, HCl and HBr

Cited by 2 publications

References 26 publications

Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study

Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study

An ab Initio Study of Linear XH−HX Hydrogen Halide Anions

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Thermal electron attachment processes in gas mixtures containing H2S, HCl and HBr

Cited by 2 publications

References 26 publications

Energetics of Br−H−Br- Formation from HBr Dimer Anion: An ab Initio Study

Energetics of Br−H−Br- Formation from HBr Dimer Anion: An ab Initio Study

An ab Initio Study of Linear XH−HX Hydrogen Halide Anions

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Product

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Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study

Energetics of Br−H−Br^- Formation from HBr Dimer Anion: An ab Initio Study