Paul H. Kasai

Electron Spin Resonance Studies of γ‐ and X‐Ray‐Irradiated Zeolites

Electron spin resonance studies have revealed the formation of superoxide ions O2− attached to the zeolitic cations when the Type Y zeolites (Lindes) are irradiated by γ and x rays in the presence of oxygen. A second unique color center was found when Na–Y zeolite was irradiated in vacuum. This center is attributed to an electron trapped within a large cavity shared among four Na+ ions.

ESR of Cu(NO3)2 and CuF2 Molecules Oriented in Neon and Argon Matrices at 4°K

An experimental apparatus is described which allows the trapping of preferentially oriented molecules in neon and argon matrices at 4°K and the measurement of their ESR spectra at various orientations relative to the magnetic field. Application to Cu(NO3)2, vaporizing at 150°C, and CuF2, vaporizing at 925°C, demonstrates that the degree of orientation is dependent upon the temperature of the vaporizing molecule and the matrix gas used. The ESR spectra of highly oriented Cu(NO3)2 in neon at 4°K (there was essentially no orientation in argon) indicate that the molecule is planar with the four nitrate oxygen atoms surrounding the Cu++ ion in a square array. The g and A values are very similar to those found in copper chelate molecules: g∥ = 2.2489±0.003, g⊥ = 2.0522±0.0005, A∥ (63Cu) = 570±3 Mc/sec, and A⊥ (63Cu) = 50±3 Mc/sec. Computer simulation of the spectra not only confirms this assignment but provides an estimate of the degree of orientation as a function of the inclination. CuF2 isolated in argon at ...

ESR Studies of Cu, Ag, and Au Atoms Isolated in Rare‐Gas Matrices

Electron spin resonance spectra were observed on Cu, Ag, and Au atoms isolated in Ne, Ar, Kr, and Xe matrices at ∼u20094°K. The hyperfine coupling constants and the g values were determined and examined for the matrix effect. With xenon matrices a superhyperfine structure with magnetic xenon nuclei was partially resolved, and by means of computer simulation, it was shown that these atoms are substitutionally incorporated within the Xe lattice. Also an evidence for atom‐vacancy pairing was observed for Cu in Ne matrix.

ESR and Optical Spectroscopy of ScO, YO, and LaO in Neon and Argon Matrices; Establishment of Their Ground Electronic States

ScO, YO, and LaO were vaporized from the solid oxides at temperatures near 2500°K and trapped in neon and argon matrices at 4° and 20°K. ESR spectra of these matrices show that the ground states of all of the molecules are 2Σ. The measured magnetic parameters for the three molecules are as follows: ScO, g=2.00±0.01, A=2.01±0.01 kMc/sec; YO, g=2.003±0.002, A=0.803±0.003 kMc/sec; LaO, g=2.01±0.01, A=3.89±0.01 kMc/sec. The A values then yield nuclear hyperfine‐structure separations (Δν) of 0.27, 0.03, and 0.52 cm−1, respectively, and explain the large splittings observed in the optical spectra of ScO and LaO.The optical spectra of the matrices exhibit the two transitions A2Π←X2Σ and B2Σ←X2Σ observed in the gas spectra of these molecules. The bands are exceptionally broad and shifted in the matrix relative to the gas, much more so than in the matrix spectra of other transition‐metal diatomic oxides. Illumination of the matrices with tungsten light leads to a gradual disappearance of the absorption bands and l...

ESR of VO in Argon Matrix at 4°K; Establishment of Its Electronic Ground State

ESR spectrum of VO isolated in argon matrix at 4°K was obtained. The analysis of the spectrum led to the unequivocal assignment of its electronic ground state as 4Σ arising from the configuration σ2π4σ1δ2. Due to the extremely large zero‐field fine‐structure splitting, the entire spectrum was found to be compatible with the effective spin Hamiltonian of the form Hu2009=u2009g‖βHzSzu2009+u20092g⊥β(HxSxu2009+u2009HySy)u2009+u2009A‖IzSzu2009+u20092A⊥(IxSxu2009+u2009IySy), with the following parameters: g‖u2009=u20092.0023u2009±u20090.001, g⊥u2009=u20091.9804u2009±u20090.001, A‖u2009=u2009714.7u2009±u20090.5 MHz, and A⊥u2009=u2009837.1u2009±u20090.5 MHz.

Electron Spin Resonance of a Center in Fluorine‐Doped Zinc Sulfide

Fluorine‐doped cubic ZnS shows a photosensitive ESR center of spin ½. The signal exhibits three types of hyperfine structures; one ascribed to a fluorine nucleus, the second to four structurally equivalent Zn+ + ions, and the third to 12 structurally equivalent Zn+ + ions. The center is, therefore, assigned to an electron excess center due to F− ion incorporated substitutionally at sulfur sites. It sets forth a direct experimental evidence that in ZnS phosphors a substitutionally incorporated halide ion could trap an electron released by photoexcitation.