Bromine Hyperfine and quadrupole fine structure in the MODR spectrum of sym-tetrabromobenzene in its lowest triplet state

Bromine hyperfine and quadrupole fine structure has been observed in the 3 cm MODR spectrum of the photoexcited ³B_1u state of symmetric tetrabromobenzene (s?TBB) in a durene host crystal at liquid helium temperature. A preliminary analysis of the observed structure yields the two in-plane values of the bromine hyperfine tensor |A_y/gβl = 10.3 and |A_z/gβ| = 16.5 (for ⁸¹Br), and a comparison of these values with those recently observed for the α-bromomaleic acid radical suggests that the correct zero-field scheme in the lowest triplet state of s-TBB is τ_N > τ_M > τ_L.     

Some predictions concerning the configurational characteristics of the vanadium-cobalt sigma phase

A simple pair-wise interaction energy model has been used to examine the possible configurational characteristics of (V-Co) as a function of composition and temperature. Near-maximum order, essentially of classic sigma-phase form, with preferential occupation of sublattices I and IV by cobalt and II by vanadium, is predicted for all compositions at room temperature. The calculations indicate significant disordering on heating, with most rapid changes in the approximate temperature range 800–1000K, but with some order remaining up to the melting point. The model results are compared with published experimental indications of transformation in this phase.Dedicated on the occasion of his 60th birthday toKurt Komarek, one of those who has shown the fascination of thermodynamic studies of ordered phases.     

The Titanium Dioxide Sensitised Photo-Oxidation of Sulphides

Titanium dioxide has been shown to photosensitise the oxidation of sulphides to give sulphoxides and sulphones. Evidence is presented against the involvement of singlet oxygen and in favour of the sulphide radical cations as being intermediates.     

Carbony- 3C hyperfine coupling tensor in 3(nπ*) benzophenone

The carbonyl- ³C hyperfine coupling tensor of ³(nπ*) benzophenone has the principal values A^C(O) = (44.7, ?11.7, ?10.9) MHz as determined by optically-detected ENDOR techniques in high field. These values are substantially less than expected for a highly-localized π-electron spin density distribution on the carbonyl fragment.     

Binding energies and bound-free transition matrix elements for an impurity atom in a hydrogen plasma

We have obtained potentials, energy levels, and bound-free transition matrix elements for an iron impurity atom in a hydrogen plasma, under varying conditions of density and temperature, according to the Thomas-Fermi (TF) and Debye-Huckel Thomas-Fermi (DHTF) statistical average-atom models. Shape resonance features in the two models are very different.     

Canonical and microcanonical calculations for fermi systems

Recursion relations are presented that allow exact calculation of canonical and microcanonical partition functions of degenerate Fermi systems, assuming no explicit two-body interactions. Calculations of the level density, sorted by angular momentum, are presented for 56Ni. The issue of treating unbound states is also addressed.     

Mixed aggregates of dilithiodiamines with alkyllithiums and lithium enolates

The formation of mixed aggregates of N,N′-dilithiodiamines with alkyllithiums and lithium enolates was investigated. Enolization of 3-pentanone with the dilithium salt of N,N′-dimethyl-1,3-propanediamine generated both the E and Z enolates and the E/Z ratio changed in the presence of a lithium enolate or excess butyllithium. The formation of mixed aggregates was modeled with the B3LYP DFT method and it was found that mixed aggregate formation is energetically favorable. The infrared spectra of dilithio-N,N′-dimethyl-1,3-propanediamine in the presence of excess butyllithium or lithium enolate are consistent with the formation of mixed aggregates.