This paper describes an investigation by ESR methods of the bonding iron-group impurity ions with configurations d3, d5, and d8 in LiF, NaF, KF, KMgF3, KCdF3. The results indicate that π σ are comparable magnitude provide evidence for relaxation ligands on to alkali halides.

Mechanical force, with its ability to distort, bend, and stretch chemical bonds, is unique in the way it activates reactions. In polymer mechanochemistry, force transduced a directional fashion, efficiency of activation depends on how well from scissile bond mechanophore (i.e., mechanochemical coupling). We have investigated effects regio- stereochemistry rate force-accelerated retro-Diels–Alder reactions furan/maleimide adducts. Four adducts, presenting an endo or exo configuration proximal...

The spin-wave dispersion relations for the simple cubic antiferromagnet RbMnF3 have been determined at 4.2 °K by inelastic neutron scattering. Spin-wave theory is used to interpret results in terms of exchange interactions 2JijSi-Sj between first, second and third neighbours with J1 = 3 4±0.3 J2 0.0±0 2 J3 0 00±0.04 °K. also confirm that anisotropy field less than 400 gauss. above value compared other experimental results, values calculated from Néel temperature. Good agreement suggests one...

Magnesium fluoride crystals can be grown in vacuo using the Stockbarger technique. The melting point is 1255 ± 3°C. crystal structure of tetragonal SnO2 type, with lattice constant a = 4.621 0.001 Å and axial ratio 1: 0.6601 0.0001 giving c 3.050 at 18°C. density 3.1766 0.0002 g cm-3

This paper describes an ESR investigation of the bonding iron-group ions with configurations d6(Fe2+) and d7(Fe+, Co2+, Ni3+) on cubic lattice sites in crystals LiF, NaF, KMgF3. To aid analysis d7 ions, optical absorption spectrum Co2+ was measured LiF A discussion is given effects dimensions charge state impurity ion parameters.

High-pressure experiments, using the piston displacement technique have been performed at temperatures down to that of liquid nitrogen on NH4I, NH4Br, ND4Br, and NH4Cl. For iodide two new phase transitions under pressure a triple point were observed. A transition observed in both bromides; existence another was confirmed. The role multipole interactions causing is discussed, basis structural data present experiments generalized diagram presented which describes gross behavior these substances.

The excitations of cobalt fluoride have been studied with the technique slow-neutron inelastic scattering. A triple-axis crystal spectrometer was used throughout in its constant Q mode operation. Several branches phonon spectra were measured and are reasonable agreement calculations based on a very simple rigid ion model. magnetic interest because Co 2+ has unpaired orbital angular momentum which gives rise to several low-lying energy levels. Excitations observed from ground state next three...

Compressions and phase diagrams for solid CO2, CS2, COS, O2, CO are presented pressures up to 10 000 atmos at low temperatures. A new modification of COS was observed under pressure.

Antiferromagnetic spin waves have been observed in a single crystal of MnF2 at 4.2°K by the inelastic scattering neutrons. Measurements were carried out using twin rotor time-of-flight spectrometer having mean incident neutron wavelength 3.00 Å and resolution (half-width half-height) 0.06 Å. Spin excited {010} plane dispersion plotted for propagation 〈100〉 〈001〉 directions. The curves can be accurately described spin-wave theory following values parameters concerned: J1=0.32°K...

The thermal conductivity of single crystals LiF containing various relative concentrations the isotopes 6Li and 7Li has been measured between 10 90 °K. An increase in resistance with isotope concentration (up to 50% either isotope) is observed, but results at 30 °K fit neither formula Klemens (1955) nor previously deduced for limit small (Berman, Foster & Ziman 1956). In a new variational treatment more general trial function used contribution phonon-phonon iV-processes calculated...

Magnetic excitations in several single crystals of the systems K(Co,Mn)${\mathrm{F}}_{3}$ and (Co, Mn)${\mathrm{F}}_{2}$ have been studied by neutron inelastic scattering. It is found that two branches well-defined magnetic excitatios, both which exhibit propagating character, occur at certain compositions. The dispersion relation for cannot be adequately described current theories, but an extension Anderson's criterion localization disordered alloys gives approximate agreement with observed...

Dispersion curves for magnons and phonons propagating in KCoF3 at low temperatures have been determined by means of neutron inelastic scattering techniques. Two branches magnetic excitations observed corresponding to a transition between the two members ground state doublet (j=1/2) Co2+ ion lowest member j=3/2 spin-orbit level. Neither branch shows evidence directional anisotropy which has suggested exchange interactions KCoF3; any splitting doubly degenerate magnon is shown be less than 8%...

The changes in the magnetic excitation spectra of MnF2 produced by increasing temperature range 0.75 TN to 1.2 have been studied neutron inelastic scattering techniques. discrete spin-wave observed a previous experiment at 4.2 °K Low et al. suffer line broadening and an energy decrease as is raised; also continuous component appears. These three effects are small about 50 (0.75 TN) but develop rapidly with temperature. However, total seen be independent up highest value used TN.

The 19F, 85Rb and 87Rb nuclear magnetic resonances observed at room temperature in single crystals of RbMnF3 are described. hyperfine interaction a fluorine nucleus with one its nearest-neighbour Mn2+ ions has axial symmetry, the principal values being A|| = (21.49 ± 0.90) × 10-4 cm-1, A⊥ (12.77 0.55) cm-1. part this which is not due to classical dipole effects been interpreted terms fraction unpaired spin F- 2s orbital (f2s (0 50 0.02)%), 2p ((fσ - fπ)2p (0.33 0 18)%). rubidium resonance...

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The solid phases of ordinary methane were studied under pressure at low temperatures by the volume discontinuity method. phase diagram is presented. A new was observed, and ``missing'' (by analogy to CD4 CD3D) evidently appears only liquid helium temperatures. Observations indicate another high pressures in low-temperature region. Indications correlations among diagrams CH4, CH3D, are shown.

The magnetic excitations of cobalt fluoride have been studied both theoretically and experimentally. theory the at low temperatures has developed with aid pseudo-boson technique in terms crystal field spin-orbit parameters individual ions exchange interactions between neighbouring ions. model surprisingly simple forms interaction gives a very good description many experimental results. Measurements longitudinal spin correlations near Neel temperature made slow neutron inelastic scattering...

A range of fluoride-encapsulated octasilsesquioxane cage compounds have been prepared using the TBAF route. Our studies suggest that whilst it is relatively straightforward to prepare with adjacent sp(2) carbons, leading a aryl and vinyl substituted compounds, corresponding sp(3) carbon derivatives are more capricious, requiring an electron withdrawing group can stabilize not acting as leaving group. Analysis by X-ray crystallography solution (19)F/(29)Si NMR spectroscopy R(8)T(8)@F(-)...

Received 1 December 1966DOI:https://doi.org/10.1103/PhysRevLett.18.162©1967 American Physical Society