Bond lengths and valences in BaBiO3

Bond length-bond strength correlations are developed for Bi(III) and Bi(V) oxides. Application to the two Bi sites in BaBiO₃ show that these are best described as Bi(III) and Bi(V) respectively, although there is a significant deviation from the ideal valence for the atom identified as Bi(III).     

Mixed state of spin moments of two protons in the water molecule and stability of its spin isomers

It is shown that the para-to-ortho water ratio most abundant in the nature is the water molecule existence form most stable to external influences. The assumptions, which are implicitly adopted when singlet and triplet states of the quantum system of two spin moments are independently considered, are discussed.     

Long range adiabatic potentials and scattering lengths for the EF,e and h states of the hydrogen molecule

Accurate EF ¹Σ _g , e ³Σ _u and h ³Σ _g state adiabatic potentials are computed for internuclear distances up to 44 atomic units. All the energies are more accurate by a fraction of a wave number from existing results. Scattering lengths for collisions of 1S and 2S hydrogen atoms are evaluated. These differ significantly from earlier results. This is because for some states the scattering length is very sensitive to even small changes in the potential.     

Rotational levels of double-minimum potentials: The linear BAB molecule with unequal bond lengths

The rotational constants and energy levels for the linear BAB system are studied under the assumption of unequal AB bond lengths. The quantum mechanical Hamiltonians is derived according to a formalism which allows for a large-amplitude antisymmetric stretching motion. A numberical integration technique is used to obtain solutions of the one-dimensional Schroedinger equation corresponding to a zeroth-order approximation of the Hamiltonian. The behavior of the resulting rotational constants for various heights of the barrier in the double-minimum potential is discussed.     

D2O‐catalyzed proton transfer selectivity of 4 different NH protons in the same molecule

When N‐benzyl‐N′‐methylacetamidinium hydrochloride (pKa=11.8) is dissolved in D₂O/DCl(1 M), an equilibrium of 2 54:46 stereoisomers in an ~2:1 =(R)N^δ+H(D) D/H ratio is formed. Therefore, 2 R =N‐benzyl (E and Z) and 2 R =N‐methyl (E and Z) groups attached to the corresponding H(D) (Z and E) for a total of 8 ¹H‐NMR signals are observed. Consequently, their rates of H and D transfer to D₂O can be measured by means of the ¹H‐NMR broadness (line shape) of the =(R )N^δ+H doublets and =(R )N^δ+D broad singlets. Acidity selectivity is observed for both processes. In fact, the relative proton and deuterium transfer rates follow the acidity order: =(PhCH₂)N^δ+‐H(E) > =(PhCH₂)N^δ+‐H(Z) > =(Me)N^δ+‐H(E) > =(Me)N^δ+‐H(Z). Proton transfer rates are in the range of 8 to 0.5 s^‐1 with α = .92. This tendency is independently supported by the observed experimental chemical shift deuterium isotopic perturbation. The rate‐limiting step for proton exchange is the breaking of the hydrogen bond due to the fast amidine reprotonation (~10¹¹ s). =(R)N^δ+D/=(R)N^δ+H equilibration is reached at ~80 s, and it can be measured by the relative =(R) N^δ+H versus =(R) N^δ+D signal integrations. The equilibrium of the 4 =(R)N^δ+H(D) centers is shifted toward deuterium, but they are further shifted in the more basic centers. Equilibrium is completely shifted toward D in the 4 centers when OD^? contributes with the exchange process at pD > 3.     

Bond lengths and bond strengths in weak and strong chemisorption: N2, CO,and CO/H on nickel surfaces

New chemical-state-specific scanned-energy mode photoelectron diffraction experiments and density functional theory calculations, applied to CO, CO/H, and N2 adsorption on Ni(100), show that chemisorption bond length changes associated with large changes in bond strength are small, but those associated with changes in bond order are much larger, and are similar to those found in molecular systems. Specifically, halving the bond strength of atop CO to Ni increases the Ni-C distance by 0.06 A, but halving the bond order (atop to bridge site) at fixed bond strength causes an increase of 0.16 A.     

On the importance of exchangeable NH protons in creatine for the magnetic coupling of creatine methyl protons in skeletal muscle

The methyl protons of creatine in skeletal muscle exhibit a strong off-resonance magnetization transfer effect. The mechanism of this process is unknown. We previously hypothesized that the exchangeable amide/amino protons of creatine might be involved. To test this the characteristics of the creatine magnetization transfer effect were investigated in excised rat hindleg skeletal muscle that was equilibrated in either H2O or D2O solutions containing creatine. The efficiency of off-resonance magnetization transfer to the protons of mobile creatine in excised muscle was similar to that previously reported in intact muscle in vivo. Equilibrating the isolated muscle in D2O solution had no effect on the magnetic coupling to the immobile protons. It is concluded that exchangeable protons play a negligible role in the magnetic coupling of creatine methyl protons in muscle.     

Causality conditions and the lengths of nonspacelike curves

In globally hyperbolic space-times there is a finite upper bound on the proper time lengths of nonspacelike curves between two chronologically related events. We show that if global hyperbolicity is replaced by a weaker causality condition, then there can exist chronologically related events in the space-time such that the proper time lengths of nonspacelike curves joining them grow without bound. We also show that the existence of a finite upper bound on the lengths of nonspacelike curves between two chronologically related events implies only chronology of the space-time but not causality.     

Probable location of a 1E2g state of the benzene molecule

Photoexcitation spectra of benzene in rare gas matrices show a previously unreported transition near 46000 cm^?1. The observed bands are not explicable in terms of site splittings, impurity states, aggregation effects, intermediate radius states of the matrix, triplet states, excimer states, exciplex states or $\text{σ-π}{}^1$ transitions. The vibronic spacings in these spectra could be those expected for a ¹E_2g ← ¹A_1g transition and on this and other evidence we argue that the ordering of origins of the first four spin allowed intravalence states of benzene is ¹B_2u (38086 cm^?1), ¹E_2g (near 46400 cm^?1), ¹B_1u (48450 cm^?1) and ¹E_1u (55430 cm^?1). Our data also show that the transition ¹B_1u ← ¹A_1g accounts for most of the intensity of the 210 nm absorption band system. Our ordering of the spin allowed states permits interpretation of experimental data of others, confirms certain semi-empirical and ab initio SCF MO CI calculations in which account is taken of higher excitations and illustrates the necessity of including such higher excitations. The intensity of the ¹E_2g ← ¹A_1g transition is at least an order of magnitude less than previously calculated indicative of the difficulty of choosing suitable wavefunctions for the ¹E_2g state and of calculating “forbidden” transition probabilities.     

Electron attenuation lengths in fullerene and fullerides

Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C₆₀ film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K₃C₆₀, K₆C₆₀, Ba₄C₆₀, Sm_2.75C₆₀ and Sm₆C₆₀ are calculated to help the quantitative analyses of the photoemission spectra for these compounds.     

Observation of beta-delayed protons in the decay of Cl

The QCD operator product expansion analysis of twist-4 effects in leptoproduction is recast as a parton model. All twist-4 corrections are expressed in terms of a limited number of multiparton (quark and gluon) longitudinal distribution functions in an infinite momentum frame.     

Acoustic peak of protons in liquids

The excitation, of acoustic emission by a pulsed beam of protons with energy Ep = 70 MeV in methanol is investigated. Growth of the acoustic signal at the end of the proton trajectory is observed. The hydrodynamic characteristics of the acoustic emission are calculated on the assumption that the sources of elastic waves in the liquids are microcavities formed at the stopping sites of slow ionization electrons, i.e., so-called electrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 91–95, August, 1977.The authors wish to thank M. F. Lomanov and Ya. L. Kleinbok for assistance with the experiment.     

Activation energy of protons in copper

The movement of protons in copper is studied using Ashcroft model potential and modified Hartree dielectric function. Octahedral position is found to be more favourable. The calculated activation energy is in good agreement with experiment for 0.31 e effective charge of the proton.     

Secondary protons in the atmosphere at different latitudes

Summary We present a semiempirical method to study the production and propagation of atmospheric secondary protons with energy>100 Mev, moving in the vertical direction. The derived production functions are fitted by the least-square method for the only previously published splash (SP) and return (RE) albedos observed data using the same instrument and measurement sites. The closed agreements between the measurement data and the calculations over a wide range of atmospheric depths lead to a possible extension of the method for other latitudes. The spectra of SP and RE intensitiesversus the geomagnetic cut-off reveal similar behaviour as assumed earlier by the theory for those components in the Earth's magnetic field.     

Correlations of two protons in relativisticdp-collisions

Two-proton correlations in thedpppn collisions of relativistic deuterons with protons are considered. These correlations give more information than inclusive proton spectra described in the framework of different deuteron structure function models because of uncertainty in the calculation of secondary interaction contribution (rescattering processes and final state interactions). We present the predictable calculations which show different behaviour of the correlation function for different deuteron structure function models in the kinematic region where contributions of secondary interactions are negligible.     

Channeling of protons,pions and deuterons in the GeV region

Strong directional effects have been observed when 1.15 and 1.35 GeV/c protons, π⁺ and π^?, and deuterons penetrate through germanium crystals. Transmission, wide-angle scattering, and an attempt to do blocking distributions are obtained from experiments using position-sensitive drift chambers. Corresponding measurements of energy loss in germanium crystals are also presented. These experimental results are compared to theory for energy loss, and satisfactory agreement is obtained.     

Dynamic shadow effect in the energy loss of protons

Summary The nonrelativistic quantum-mechanical approach for the stopping power has been developed by means of the Glauber-Franco approximation for the inelastic-scattering amplitude. It takes into account excitation and ionization processes in the amorphous target by heavy charged particles. The calculations of the stopping power of protons in H and He targets are in excellent agreement with the available experimental data due to the effect of nuclear dynamic blocking (shadow) and the rescattering processes by the electrons of the target atom. Formulae of the stopping-power calculations, taking into account individual atom shell effects, have been derived. On this basis, the case of violation of Bragg’s additivity rule is discussed.