High-pressure ESR Research Articles

Metal–insulator transition in the one-dimensional organic conductor (TSM-TTP)(I 3) 5/3

(TSM-TTP)(I 3) 5/3 (TSM-TTP: 2,5-bis[4,5-bis(methylseleno)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene) is a one-dimensional organic conductor which undergoes a metal–insulator transition at T MI≈20 K. High pressure resistivity, ESR, and static magnetic susceptibility measurements have been carried out to clarify the origin of the metal–insulator transition. The metal–insulator transition temperature is not completely suppressed even under a pressure of 11.8 kbar. The ESR line shape shows no anomaly and the magnetic susceptibility shows a slight increase below 70 K, and remains paramagnetic down to 1.75 K; no evidence of spin-Peierls or antiferromagnetic transition is obtained.

Pressure-resisting glass cell for high-pressure ESR measurements

The authors have described a pressure-resisting glass cell with which high-resolution ESR measurement of liquid samples under pressures up to 900 bar can be carried out on an ordinary high-resolution spectrometer. Recent investigations at high pressures have been presented.

ESR Studies at High Pressures. III. Spin-Exchange Reactions of Some Nitroxide Radicals in Acetone and Hexane

Abstract Pressure effects on the rate of spin–spin exchange of some nitroxide radicals in acetone and hexane at 298.2 K have been studied by means of a high-pressure ESR technique. It was found that this exchange reaction is diffusion-controlled. The rate of the spin exchange is related to that of diffusion, the probability of the spin exchange, P=f(J, τ1), and steric factor fs. The values of P and hence τ1 were estimated as a function of pressure. A method for evaluating the steric factor and the exchange integral is proposed.

High temperature, high pressure ESR study of molybdenum-containing catalysts

The reduction of molybdenum in molybdenum trioxide over various supports was studied using high-temperature, high-pressure ESR techniques. The support materials have a great influence on the reduction behaviour of the catalysts at high temperatures under a high pressure of hydrogen. The ease of reduction of molybdenum in the order MoO3/SnO2 > MoO3/ZrO2 > MoO3/TiO2 > MoO3/Al2O3 > MoO3/SiO2 > MoO3/MgO.To clarify the interaction between catalysts and reactants, the molybdenum-containing catalyst-9-methylanthracene system was monitored. An electron-transfer reaction from 9-methylanthracene to catalysts occurred and both organic radicals and Mo(V) species were observed at the same time. It was found that the behaviours of organic radicals and Mo(V) species depend on the support materials, i.e. the organic radical concentration increases with increasing Mo(V) concentration for the MoO3-Al2O3-9-methylanthracene system in the temperature range 381 – 558 K. On the other hand, the organic radical concentration is inversely proportional to Mo(V) concentration for the MoO3-ZrO2-9-methylanthracene system in the range 399 – 493 K.

High-pressure high-temperature ESR in early stage of carbonization of pitch

Description d'une cellule de spectrometrie RSE a haute pression et temperature. Application de celle-ci a l'etude de la variation de la concentration des spins au cours de la carbonisation de la fraction soluble dans la pyridine d'un brai de petrole au cours de sa carbonisation entre 300 et 800°C sous differentes pressions d'azote et d'hydrogene

High-pressure ESR investigation of Cu 2+ in ND 4Cl single crystals

ESR spectra of Cu 2+ ions in ND 4Cl single crystals have been measured as a function of pressure and temperature in the region of the order-disorder phase transition and the spin hamiltonian parameters g |, g ⊥, A, B, P | have been determined. The behaviour of the hyperfine constant A is discussed in more detail. It is concluded that the change in lattice parameter is at least partly responsible for the anomalous change in the hyperfine parameters at the λ-point.