Moment functions of the hydrogen molecular ion

The moment functions of H⁺₂ are computed for internuclear distances up to 5a₀ from the dipole osciliator strengths.     

The mechanism of hydrogen randomization in the stilbene molecular ion

Hydrogen randomization of the stilbene molecular ion preceding the formation of the [M—methyl]-ion is discussed.     

An algorithm for the use of symmetry in molecular self-consistent-field calculations

The application of a simple relationship between atomic orbital integrals and symmetry orbital integrals is described in connection with traditional uses of symmetry. The simple modifications for implementation in the POLYATOM molecular self-consistent-field programs are given and discussed. Examples of the effectiveness of these modifications are included.     

Acidic and basic molecular hardness in LCAO approximation

Hardness of a molecule has been formulated as an average of a set of terms representing various types of reactivity. Hardness parameters for molecules and bonded atoms have been calculated by the ab initio Hartree-Fock self-consistent field (HF SCF) method. An analysis has been presented of the correlation between the relative magnitude of contributions to the total hardness and experimentally observed acidic or basic reactivity of molecules. © 1997 John Wiley & Sons, Inc.     

Ring expansion and hydrogen scrambling in the molecular ion of 3-methylthiophene

The ratio [M ? D]/{[M-D] + [M ? H]} in the 70 eV mass spectra of six deuterated 3-methylthiophenes has been determined. From these values the mole fractions of the molecular ions that lose hydrogen atoms specifically from the various positions of the molecule were calculated, as well as the mole fraction in which the hydrogen atoms are fully scrambled before hydrogen elimination. It appears that hydrogen atoms are mainly lost from a fully scrambled [C₅H₆S]⁺· ion and from the α-position of the original molecular ion. A deuterium isotope effect of 1·60 to 1·72 was calculated for the hydrogen elimination. The reaction was also studied at low electron energies. In order to determine the degree of scrambling in the [C₅H₅S]⁺ ions, some decomposition reactions of this ion were investigated.     

Approximated dynamical symmetry of two-electron atoms

the eigenstates of a new set of approximate constants of the motion of two-electron atoms are very nearly those obtained by diagnolizing 1/r_ij within a complex. They easily obtained by reducing SO(4) × SO(4) to SO(4) in a novel way.     

Bethe logarithm and Lamb shift for the hydrogen molecular ion

A variational method is used to evaluate Bethe logarithm for the ground electronic state of the hydrogen molecular ion. The trial function employed in the calculations analytically represents the singular behavior of the exact solution of the variational problem for high virtual photon energies. This ensures that the accuracy of six significant figures can be obtained with basis sets not exceeding 70 functions. For the equilibrium internuclear separation of 2.0 bohr, the calculated value of the Bethe logarithm, equal to 2.31936, lies outside the bounds 2.35 and 2.56, representing the best previous estimation of this quantity. The accurate values of the Bethe logarithm for internuclear separations ranging from 0.6 to 6.0 bohr are tabulated and used to calculate the radiative corrections to the rovibrational energy levels of H₂⁺, HD⁺, and D₂⁺. The influence of these corrections on the transition and dissociation energies is also examined.     

On the rearrangement and scrambling of hydrogen in the benzophenone oxime molecular ion

The losses of CO, hydrogen and CO, OH and HNOH radicals from the benzophenone oxime molecular ion have been studied by means of deuterium labelled compounds. Hydrogen scrambling and/or exchange and rearrangement reactions of interest, taking place prior to fragmentation, were observed.     

Photodissociative formation of ion pairs from molecular hydrogen and the electron affinity of the hydrogen atom

Photodissociative production of ion pairs from H₂ has been observed in the wavelength range 706–718 A at spectral resolution of 0.4 and 0.22 A. From measured thresholds for production of H^? from H₂ molecules in each of the three lowest rotational states, the lower bound EA(H) ? 0.754 ± 0.002 eV is obtained, in excellent agreement with the theoretical electron affinity of 0.75421 eV. For formation of D^? from D₂, a threshold assigned to molecules in the rotational state J = 2 has been measured, from which the bound EA(D) ? 0.757 ± 0.005 eV is obtained. Negative ion yield curves are presented for hydrogen.     

Scrambling in ethane molecular ion: An INDO model for hydrogen exchange before mass spectral fragmentation

INDO calculations for previously proposed activated complexes for scrambling in ethane molecular ion suggest that the structure equivalent to diborane is more stable than one in which hydrogens on the same side of the molecule exchange positions.     

An electrode for the coulometric generation of hydrogen ion

The anodic generation of hydrogen ion on bright platinum in 1.0M sodium perchlorate is not quantitative owing to the formation of a chemical species With oxidizińg properties, presumably a peroxydiperchlorate, but 100% current efficiency can be obtained in the anodic generation of hydrogen in 0.25M sodium hydrazinium sulphate, Na(N(2)H(5))SO(4). Five hydrogen ions are formed for each four electrons passed. The efficiency of this "hydrazine-platinum anode" has been demonstrated by the high-precision coulometric titration of tris(hydroxymethyl)aminomethane.     

Permutation representations in molecular symmetry

The reducible representations of the point groups are generally studied because of their relevance to molecular orbital and vibration theory. Triple correlations within the polyhedra are described by group-theoretical invariants that are related to the permutation representations and termed polyhedral isoscalar factors. These invariants are applied in theorems on matrix elements referring to the symmetry-adapted bases at different centres. Further invariants or geometrical weight factors inter-relate different types of reduced matrix elements of irreducible tensors (generalization of the Wigner-Eckart theorem to the polycentric case). As a demonstration a complete tabulation is given for the point group C ₄.     

Structural and dynamical properties of the Hg2+ aqua ion: a molecular dynamics study

Molecular dynamics simulations of the Hg2+ ion in aqueous solution have been carried out using an effective two-body potential derived from quantum mechanical calculations. A stable heptacoordinated structure of the Hg2+ first hydration shell has been observed and confirmed by extended X-ray absorption fine structure (EXAFS) experimental data. The structural properties of the Hg2+ hydration shells have been investigated using radial and angular distribution functions, while the dynamical behavior has been discussed in terms of reorientational correlation functions, mean residence times of water molecules in the first and second hydration shells, and self-diffusion coefficients. The effect of water-water interactions on the Hg2+ hydration properties has been evaluated using the SPC/E and TIP5P water models.     

Determination of the molecular symmetry in crystalline germane

The symmetry of the germane molecule in the various crystalline phases of solid germane has been investigated using the IR spectrum of the isotopically dilute GeH₃D molecule. The observed spectra indicate that the cubic crystal symmetry of the higher-temperature phases is lost in phase III and possible site symmetries are proposed. Band broadening is found in phase I and is interpreted as arising from rapid molecular reorientation.     

The long-lived molecular ion of propionitrile: An ion cyclotron resonance study

Evidence has been reported that primary loss of H and of HCN from the molecular ions of propionitrile, isobutyronitrile and butyronitrile in the mass spectrometer is preferentially preceded by hydrogen migration from C-2 to C-1. Ion cyclotron double resonance spectra of proton (or deuteron-) transfer products derived from propionitrile-2-d2 and -3-d3 and a series of bases provide evidence that such migration occurs also in long-lived propionitrile molecular ions.