μSR study of RNi5 intermetallics where R=La,Gd or Tb

Zero-field μSR studies of some hexagonal intermetallic compounds are described. Our LaNI₅ data provide information on the muon localisation site. This site could be one of the deuterium sites deduced from neutron diffraction. A comparison of the temperature dependence of the exponential damping rate, λ(T), of our samples shows that λ(T) is strongly influenced by crystal field effects. The TbNi₅ spectra exhibit two components forT<60 K. We discuss the possible explanations of this result. We see a μSR signal below the magnetic phase transition in GdNi₅. This makes the study of the spin-lattice relaxation rate possible in the ordered magnetic state.     

Infrared spectra and intermolecular potentials of matrix isolated methyl nitrate and methyl-d3-nitrate

The infrared spectra of protonated and deuterated methyl nitrate isolated in a nitrogen matrix have been recorded from 4000 to 250 cm⁻¹. Peaks have been assigned to monomers, pairs, and higher-ordered species by varying the concentration of methyl nitrate in the matrix and also by inducing diffusion of molecules in the matrix. Monomer frequencies were used to calculate the normal coordinates, force constants, and cartesian displacements. Configurations of a pair of methyl nitrate molecules were calculated using an approximate nonbonded atom-atom potential including both Lennard-Jones and electrostatic potentials. The position of minimum energy was established as a function of the distance between molecules as well as angular rotation of the two molecules with respect to one another. Calculations of exciton splittings and shifts for the pair configuration computed to be most stable were evaluated by two site exciton theory and compared to the assigned pair frequencies.     

Energy transfer by intranuclear cascade of pi-zeros produced in antiproton annihilation at rest in nuclear targets

The energy transfer by pi-zeros in the intranuclear cascade initiated by antiproton annihilation at rest in carbon and uranium has been measured to be 28 ± 43 and 232 ± 33 MeV respectively. We estimate the total energy transfer due to all pions to be 75 ± 53 and 447 ± 42 MeV respectively. The uranium value is ～ 17% larger than a recent theoretical prediction. No predictions for carbon are available. Given the expected increase in efficiency of energy transfer from antiproton beams at ～ 3 GeV/c momentum, the prospects for initiating multifragmentation and disintegration of heavy nuclei at these energies appear good.     

The direct pair correlation function of liquid indium

The static structure factor S(k) of liquid indium has been measured accurately down to $\text{k = 0.8}\text{A}\text{?}{}^{\mathrm{?1}}$ using CuKα radiation with reflection geometry. The direct pair correlation function in k space is analyzed to demonstrate the utility of this technique in reducing errors in the resulting direct pair correlation function in configuration space.     

Asymmetry of the Van der Waals interaction between a molecule and a surface

The asymptotic molecule-surface Van der Waals interaction is found to depend on the orientation of the molecular axis because of the asymmetry of the molecular polarizability and the angle-dependence of the surface response to a dipole field. This orientation dependence can cause rotational transitions in a beam of molecules directed at the surface, and contributes to the splitting of rotational levels within a given multiplet when a molecule is physisorbed. An estimate of this splitting is given for H₂.