Hydrogen Halide Molecules Research Articles

Acid Dissociation in (HX)n (H2 O)n Clusters (X=F, Cl, Br, I; n=2, 3).

In this work, we analyze the interactions between two or three hydrogen halide molecules and the same number of water moieties through a systematic exploration of their potential energy surfaces. Our results indicate that the most stable HF and HCl aggregates do not experience dissociation of any of the acid fragments, even with three water molecules. In contrast, in the HBr and HI clusters, one of the acid fragments does dissociate. While the global minimum of (HBr)3 (H2 O)3 is a hydrogen-bridged bihalide anion (BrHBr- ), which is persistent at temperatures up to 203 K, the lowest energy structure of (HI)3 (H2 O)3 has a separated ion pair, but the motif with a bihalide anion (IHI- ) is only 0.2 kcal mol-1 above the global minimum. Among the more stable structures is a broad spectrum of contacts, including water⋯water, HX⋯water, and HX⋯HX hydrogen bonds, halogen bonds, ionic and long-range X⋯H contacts.

Spin-polarized proton beam generation from gas-jet targets by intense laser pulses.

A method of generating spin-polarized proton beams from a gas jet by using a multipetawatt laser is put forward. With currently available techniques of producing prepolarized monatomic gases from photodissociated hydrogen halide molecules and petawatt lasers, proton beams with energy ≳50 MeV and ≈80% polarization are proved to be obtained. Two-stage acceleration and spin dynamics of protons are investigated theoretically and by means of fully self-consistent three-dimensional particle-in-cell simulations. Our results predict the dependence of the beam polarization on the intensity of the driving laser pulse. Generation of bright energetic polarized proton beams would open a domain of polarization studies with laser driven accelerators and have potential application to enable effective detection in explorations of quantum chromodynamics.

Computational studies of boron- and nitrogen-doped single-walled carbon nanotubes as potential sensor materials of hydrogen halide molecules HX (X = F, Cl, Br)

Potential applicability of undoped, B-, and N-doped carbon nanotubes (CNTs) for elaboration of the working materials of gas sensors of hydrogen halide molecules HX (X = F, Cl, Br) is analyzed in computational studies of molecular adsorption on the CNTs surfaces. Density Functional Theory (DFT)-based geometry-optimized calculations of the electronic structure of undoped, B-, and N-doped CNTs of (3,3) and (5,5) chiralities with adsorbed HX (X = F, Cl, Br) molecules are performed within molecular cluster approach. Relaxed geometries, binding energies between the adsorbates and the nanotubes, charge states of the adsorbates and the electronic wave function contours are calculated and analyzed in the context of gas sensing applications. Obtained results are supplemented by calculations of adsorption of hydrogen halides on B(N)-doped graphene sheets which are considered as model approximation for large-diameter CNTs. It is found that the B-doped CNTs are perspective for elaboration of sensing materials for detection of HCl and HBr molecules. The undoped and the N-doped CNTs are predicted to be less suitable materials for detection of hydrogen halide gases HX (X = F, Cl, Br). © 2015 Wiley Periodicals, Inc.

Interaction of N-hydroxyurea with strong proton donors: HCl and HF

An infrared spectroscopic and MP2/6-311++G(2d,2p) study of strong hydrogen bonded complexes of N-hydroxyurea (NH2CONHOH) with hydrogen halides (HCl and HF) trapped in solid argon matrices is reported. 1:1 and 1:2 complexes between N-hydroxyurea and hydrogen chloride, hydrogen fluoride have been identified in the NH2CONHOH/HCl/Ar, NH2CONHOH/HF/Ar matrices, respectively; their structures were determined by comparison of the spectra with the results of calculations. In the 1:1 complexes, identified for both hydrogen halide molecules, the cyclic structure stabilized by the X–H⋯O and N–H⋯X bonds is present; for the NH2CONHOH⋯HF system another isomeric 1:1 complex is also observed. Two 1:2 complexes were identified for the N-hydroxyurea–hydrogen chloride system characterised by the Cl–H⋯O and N–H⋯Cl bonds. The results of the study evidence that N-hydroxyurea is an oxygen base in the gas-phase with the carbonyl group as the strongest proton acceptor centre in the molecule.

Local unitary transformation method toward practical electron correlation calculations with scalar relativistic effect in large-scale molecules

In order to perform practical electron correlation calculations, the local unitary transformation (LUT) scheme at the spin-free infinite-order Douglas-Kroll-Hess (IODKH) level [J. Seino and H. Nakai, J. Chem. Phys. 136, 244102 (2012); and ibid. 137, 144101 (2012)], which is based on the locality of relativistic effects, has been combined with the linear-scaling divide-and-conquer (DC)-based Hartree-Fock (HF) and electron correlation methods, such as the second-order Mo̸ller-Plesset (MP2) and the coupled cluster theories with single and double excitations (CCSD). Numerical applications in hydrogen halide molecules, (HX)n (X = F, Cl, Br, and I), coinage metal chain systems, Mn (M = Cu and Ag), and platinum-terminated polyynediyl chain, trans,trans-{(p-CH3C6H4)3P}2(C6H5)Pt(C≡C)4Pt(C6H5){(p-CH3C6H4)3P}2, clarified that the present methods, namely DC-HF, MP2, and CCSD with the LUT-IODKH Hamiltonian, reproduce the results obtained using conventional methods with small computational costs. The combination of both LUT and DC techniques could be the first approach that achieves overall quasi-linear-scaling with a small prefactor for relativistic electron correlation calculations.

Interactional potential of helium atom and hydrogen halide molecules

According to ab initio calculations, the differential scattering cross sections between He and HF, HCl, HBr are calculated and compared with experimental data. The results show that the calculation method can calculate comparatively accurate interactional potential. As halogen atom radius increases, at 0°, the minimum of interactional potential shallows, the position of potential well moves into the distance, and anisotropic property becomes prominent, while at 180°, the minimum of interactional potential depens, the position of potential well moves into the distance, and the isotropic property becomes obvious. The potential well depth under T structure is larger than that of linear structure. With the increases of halogen atoms radius, a more spherical symmetry is exhibited, and it can be seen obviously that contributions of radial coefficients V0, V1, V2, V3, ··· decrease gradually, which is important to understand the study of excited state dynamics.

Local unitary transformation method for large-scale two-component relativistic calculations. II. Extension to two-electron Coulomb interaction

The local unitary transformation (LUT) scheme at the spin-free infinite-order Douglas-Kroll-Hess (IODKH) level [J. Seino and H. Nakai, J. Chem. Phys. 136, 244102 (2012)], which is based on the locality of relativistic effects, has been extended to a four-component Dirac-Coulomb Hamiltonian. In the previous study, the LUT scheme was applied only to a one-particle IODKH Hamiltonian with non-relativistic two-electron Coulomb interaction, termed IODKH/C. The current study extends the LUT scheme to a two-particle IODKH Hamiltonian as well as one-particle one, termed IODKH/IODKH, which has been a real bottleneck in numerical calculation. The LUT scheme with the IODKH/IODKH Hamiltonian was numerically assessed in the diatomic molecules HX and X(2) and hydrogen halide molecules, (HX)(n) (X = F, Cl, Br, and I). The total Hartree-Fock energies calculated by the LUT method agree well with conventional IODKH/IODKH results. The computational cost of the LUT method is reduced drastically compared with that of the conventional method. In addition, the LUT method achieves linear-scaling with respect to the system size and a small prefactor.

Comparison in the complexes of oxygen-containing σ-electron donor with hydrogen halide and dihalogen molecules

Ab initio and “Atoms in Molecules” studies have been carried on the intermolecular interactions between oxygen-containing σ-electron donors B (B = H 2O, H 2CO, (CH 2) 2O) and hydrogen halide HY and dihalogen molecules XY (X, Y = F, Cl, Br). The geometries, energies and topological characteristics of hydrogen-bonded systems have been compared with those of halogen-bonded systems. In general, many properties of the halogen bond are analogous to those of the hydrogen bond. For the same electron acceptor H or X atom, the properties such as bond distance, binding energy, electron density and charge transfer decrease in the sequence of B···HF > B···HCl > B···HBr, B···ClF > B···Cl 2, B···BrF > B···BrCl > B···Br 2. The bond distance, frequency shift and electron density may be applied as the measure of strength of hydrogen and halogen bond. The decrease in the atomic dipolar polarization and the atomic volume are dependent of the strength of halogen-bonded interaction, while they are independent of the strength of hydrogen-bonded interaction.

Ionization cross sections by electron impact on halogen atoms, diatomic halogen and hydrogen halide molecules

The binary-encounter-Bethe (BEB) model has been used to calculate electron-impact ionization cross sections of Br, I, Br2, I2, HCl, HBr and HI. The BEB single ionization cross sections of Br and I presented here agree generally well with experimental results with respect to low- and high-energy behaviour and peak values. In view of this generally good agreement, the BEB cross sections of the other molecules, for which no experimental results are available, are also expected to be reliable. We compare our results with those from alternative models, where available. We also explore the use of effective core potentials for the heavy atoms of these molecules within the context of the BEB model.

Emergence of Charge-Transfer-to-Solvent Band in the Absorption Spectra of Hydrogen Halides on Ice Nanoparticles: Spectroscopic Evidence for Acidic Dissociation

Extensive ab initio calculations complemented by a photodissociation experiment at 193 nm elucidate the nature of hydrogen halide molecules bound on free ice nanoparticles. Electronic absorption spectra of small water clusters (up to 5 water molecules) and water clusters doped with hydrogen fluoride, hydrogen chloride and hydrogen bromide were calculated. The spectra were modeled at the time-dependent density functional (TDDFT) level of theory with the BHandHLYP functional using the reflection principle. We observe the emergence of a charge-transfer-to-solvent (CTTS) band in the absorption spectra upon the acidic dissociation of the hydrogen halides. The CTTS band provides a spectroscopically observable feature for the acidic dissociation. The calculated spectra were compared with our new experimental photodissociation data for larger water clusters doped with HCl and HBr. We conclude that HCl and HBr dissociate to a large extent on the surface of ice nanoparticles at temperatures near 120 K and photoactive products are formed. The acidic dissociation of HX leads to an enhancement by about 4 orders of magnitude of the HCl photolysis rate in the 200-300 nm region, which is potentially relevant for the halogen budget in the atmosphere.

Inner-shell photoionization of molecules using a two-dimensional imaging technique

Angle resolved two-dimensional photoelectron spectroscopy has been used to study resonances corresponding to inner-shell excitation in hydrogen halide molecules. In HBr 3d → σ* excitations have been studied, whilst in HCl and DCl 2p → σ* resonances have been explored. In HBr the photon energy positions of the two 3d5/2,3/2 → σ* resonances have been measured directly. Atomic Br is produced following dissociation of the σ* state and the asymmetric photon energy profile of Br atomic Auger lines is discussed. Angular distribution parameters of Br Auger lines have also been measured. In HCl and DCl the comprehensive nature of the analogous 2DPES reveal unexpected spectral features, the origin of which is considered.

Rhenium(V) complexes with sulfur-containing amino acids

Rhenium(V) complexes with 2-amino-4-(methylthio)butanoic acid (methionine, Met) and 2-amino-3-sulfopropionic acid (cysteine, Cys) have been synthesized. Depending on the initial reagent ratio, the resulting complexes contain one or two ligand molecules. On heating the compounds with one amino acid molecule, two hydrogen halide molecules are removed at 128–132°C to form a molecular complex. The composition, structure, and thermal stability of the complexes have been studied by elemental analysis, conductometry, IR spectroscopy, NMR, and mass spectrometry.

Theoretical Investigations of Vibrational – Rotational Energy of some Hydrogen Halide Molecules

A theoretical study by using computer model is presented to study the energy characteristics of the vibrational – rotational levels as a function of the vibrational and rotational quantum number, respectively. The calculations were based on the basis of a multilevel model taking into account the non-equilibrium population of the rotational levels. The computational investigation has been performed to examine the vibrational-rotational characteristics of some hydrogen halides chemical laser molecules. This program takes into account the various molecules of chemical lasers such as, Hydrogen Fluoride (HF), Deuterium Fluoride (DF), Hydrogen Chloride (HCl), and Deuterium Chloride (DCl). The practical difficulties associated with this type of lasers suggested that alternative route might be quite useful. Thus particular attention was paid to the development of computer program to investigate various energy characteristics. Comparison of the calculated results for different molecules shows that the highest values for the HF molecule probably due to their higher constants in comparison with the other molecules.

Theoretical Investigations of Vibrational – Rotational Energy of some Hydrogen Halide Molecules

A theoretical study by using computer model is presented to study the energy characteristics of the vibrational – rotational levels as a function of the vibrational and rotational quantum number, respectively. The calculations were based on the basis of a multilevel model taking into account the non-equilibrium population of the rotational levels. The computational investigation has been performed to examine the vibrational-rotational characteristics of some hydrogen halides chemical laser molecules. This program takes into account the various molecules of chemical lasers such as, Hydrogen Fluoride (HF), Deuterium Fluoride (DF), Hydrogen Chloride (HCl), and Deuterium Chloride (DCl). The practical difficulties associated with this type of lasers suggested that alternative route might be quite useful. Thus particular attention was paid to the development of computer program to investigate various energy characteristics. Comparison of the calculated results for different molecules shows that the highest values for the HF molecule probably due to their higher constants in comparison with the other molecules.

Partial Wave Cross Sections for Collisions between HeliumAtoms and Hydrogen Halide Molecules

The close-coupling method is utilized to calculate partial crosssections for elastic and inelastic scattering of He atoms with HX (X=F,Cl, Br) molecule based on the CCSD (T) potential energy surfacesobtained in the previous research. The calculation is performed at theincident energy of 200 meV. The rationality of our results has beenconfirmed by comparison with the available theoretical results. Thetendency of the elastic and inelastic rotational excitation partialwave cross sections varying with the reduced mass of the three systemsis obtained.

Pressure broadening and shifting parameters for the spectral lines in the fundamental vibration–rotation bands of HBr and HI in mixtures with rare gases

We report measurements of the line broadening and shifting coefficients in the (1 ← 0) fundamental absorption bands of the HBr and HI molecules in mixtures with rare gases He, Ne, Ar, Kr, and Xe. Comparison is given with the published data on other HHal–Rg systems. The measured line shifts are separated into terms symmetric and asymmetric in the line number m. The magnitudes of the symmetric shifts change in a regular manner in the series of rare gases and reach perturber-specific asymptotic values at higher ∣ m∣. It is found that the asymptotic values of the symmetric line shifts linearly correlate with the respective C 6 potential energy constants and that the slopes of these correlations are proportional to the vibrational ground state dipole moments squared of the hydrogen halide molecules.

Electron Impact Ionization of Haloalkanes in Helium Nanodroplets

Electron impact (EI) mass spectra of a selection of C1-C3 haloalkanes in helium nanodroplets have been recorded to determine if the helium solvent can significantly reduce molecular ion fragmentation. Haloalkanes were chosen for investigation because their EI mass spectra in the gas phase show extensive ion fragmentation. There is no evidence of any major softening effect in large helium droplets ( approximately 60 000 helium atoms), but some branching ratios are altered. In particular, channels requiring C-C bond fission or concerted processes leading to the ejection of hydrogen halide molecules are suppressed by helium solvation. Rapid cooling by the helium is not sufficient to account for all the differences between the helium droplet and gas phase mass spectra. It is also suggested that the formation of a solid "snowball" of helium around the molecular ion introduces a cage effect, which enhances those fragmentation channels that require minimal disruption to the helium cage for products to escape.

NIST-JANAF Thermochemical Tables. III. Diatomic Hydrogen Halide Gases

The spectroscopic and thermodynamic properties of the four diatomic hydrogen halide molecules—HX(g), where X=F, Cl, Br, and I—have been reviewed. Four revised thermochemical tables result from this critical review. The revisions involved the consideration of new spectroscopic information and the use of a direct summation over states for the generation of the thermochemical tables. Compared to previous calculations, the entropies at 298.15 K are unchanged, but the high temperature values (T>4000 K) are significantly different.

Infrared matrix isolation studies of the acetohydroxamic acid complexes with HF and HCl

Argon matrix infrared spectra of the complexes formed between acetohydroxamic acid (CH 3CONHOH) and hydrogen halides (HF, HCl) have been recorded. The experimental results indicate formation of a strong binary complex in which the hydrogen halide molecule acts as a proton donor towards the carbonyl group of acetohydroxamic acid. The H–X stretches and several perturbed CH 3CONHOH vibrations were identified for the two HX complexes; for the HF complex the two librational HF modes were also observed.

Search for oriented HXeX molecules from the photolysis of HCl and HBr in xenon clusters

The orientation of free HRgX molecules arising from photodissociation of hydrogen halide molecules HX on rare gas clusters Rgn is investigated in a new experimental arrangement: the rare gas cluster beam with HX molecules in the surface is intersected by two focussed laser beams at one point, where it additionally interacts with a weak electrostatic field. The possibility to generate and successively orient this new class of molecules is analyzed for a couple of new candidate molecules. We observe oriented HXeCl molecules, while HXeBr and HKrCl escaped our detection scheme, as was expected from the analysis. Details of the measured kinetic energy distributions (KED) of H-fragment atoms from the HXeCl photodissociation are analyzed in terms of the Xe–H vibrational structure on the calculated potential energy surface of HXeCl. Finally, a strong indication for observation of HXeH molecules is found in the fragment KED peak around 0.35 eV. These symmetric molecules arise from the dissociation of more than one HX molecule on the cluster and are consistently observed for all HX–Xen systems with X=Cl,Br,I.