Electron spin resonance studies of radiation effects in inorganic solids

Abstract

Defects induced in magnesium oxide by neutron irradiation are largely the result of atom displacements. The vacancies which are left behind are sites at which either electrons or holes may be trapped, depending upon the sign of the displaced ion. Such bound electrons or holes are paramagnetic entities which may give rise to e.s.r. absorption. We suggest that negative-ion vacancies in three different environments are trapping sites for electrons, and positive-ion vacancies of two types are trapping sites for holes. These two hole centres are in addition to those types found in crystals which have not been neutron-irradiated. Some of these centres may be induced by grinding and X-irradiation of MgO or other alkaline earth oxides, sulphides or selenides which have the MgO structure. Mechanical working is believed to distribute negative-ion vacancies by dissociation from dislocations which are swept through the crystals. In the neutron-irradiated crystals, there is evidence that some local regions are so disrupted that they rearrange to bodycentred instead of face-centred packing. Extended heating largely anneals out the neutronproduced structural defects. One is then enabled to see e.s.r. spectra of defects which are highly sensitive to distortions of cubic symmetry.

Spin States of C603-and C120On-(n= 2, 3, 4) Anions Using Electron Spin Transient Nutation Spectroscopy

“…15 Relative to the F + line, the g-factor for DPPH was 2.0037 with an estimated uncertainty of (0.0003, the same as the published value. 16 Pulsed EPR.…”

The temperature dependence of the F band in magnesium oxide

“…At higher doses other bands are observed overlapping the F band (Henderson and King 1966). These bands may be related to the defect clusters detected earlier using paramagnetic resonance (Henderson 1966, Wertz et al 1961. The F-centre concentration was, however, sufficiently high for the F band to dominate in the ultra-violet region of the spectrum.…”

Copper-mediated Amyloid-β Toxicity Is Associated with an Intermolecular Histidine Bridge

“…Spectra acquired at 2.5 K using the ESP380E were achieved using an Oxford Instruments CF935 cryostat with an ER4118 cylindrical cavity insert. The microwave frequency was measured with an EIP microwave 548A frequency counter, and the g factors were determined with reference to the F ϩ line in CaO (19). Spectrum simulations were performed with the SOPHE software (version 1.1.4) described by Hanson et al (20).…”