The experimental structure of199Au and the interacting boson-fermion model

Gamma rays of¹⁹⁹Au obtained after double neutron capture in¹⁹⁷Au were measured at the ILL high flux reactor. A level scheme up to 1770 keV excitation energy is established. The result is compared with IBFM and Boson-Fermion-Symmetry calculations.     

Latex Fractionation by Sedimentation and Colloidal Crystallization: The Case of Poly(styrene-co-acrylamide)

Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press.     

Structure of the Triplet of low-lying states in101Mo

The properties of the triplet of low-lying states in¹⁰¹Mo have been studied through spectroscopy of theγ radiation following thermal neutron capture in¹⁰⁰Mo and β^? decay of¹⁰¹Nb and through a measurement of the proton angular distributions in the¹⁰⁰Mo(d,p) reaction with 14 MeV deuteron energy. The half-lives of the 13.5 keV state and the 57.0 keV 5/2⁺ state have been measured as 226(7) and 133(7)ns, respectively. These values and the quadrupole/dipole mixing ratios of the 13.5 keV and 43.5 keV transitions yield spin and parity 3/2⁺ for the 13.5 keV level. The E2 components in the 13.5 (3/2⁺ →1/2⁺) and 43.5 keV (5/2⁺→3/2⁺) transitions are ≦ 8·10^?4 and 54(9)%, respectively. The possibility of an additional state near to the 57.0 keV level is discussed. IBFM/PTQM calculations, taking into consideration the transitional character of the¹⁰⁰Mo boson core, account for the electromagnetic-transition and transfer-reaction pattern of the triplet of states.     

Studies on TMPD:TCNB; a donor-acceptor with room temperature paramagnetism and n-pi interaction

A donor-acceptor compound based on N,N,N',N'-tetramethyl-p-phenylene-diamine and 1,2,4,5-tetracyanobenzene (TMPD:TCNB) has been synthesized. The crystal structure of the black 1:1 complex formed between TMPD and TCNB has been determined by single crystal X-ray diffraction at room temperature. The compound crystallizes in the triclinic space group P-1 with cell dimensions: a = 7.4986(15) ?, b =7.6772(11) ?, c = 8.0764(15) ?, alpha = 78.822(12) degrees, beta = 83.3779(19) degrees, gamma = 86.289(17) degrees .TMPD and TCNB molecules are stacked alternately in infinite columns along the a-axis. The structure does not seem to show the usual pi-pi interaction between the two aromatic rings, but indicates an n-pi interaction localized between the nitrogen atoms of the donor and the cyano groups of the acceptor.     

Magnetization and EPR of a series of Cr squarate dimers

A series of Cr(III) dimers were synthesized from a parent compound [Cr₂(μ-oxo)₂(μ_1,2-C₄O₄)₂(H₂O)₄]·2H₂O (I) by ligand substitution. The compounds have been analyzed using variable frequency EPR (9–110 GHz) and magnetic susceptibility as a function of field (0–9 T) and temperature (1.9–300 K) to obtain their electronic g-values, exchange energies, and zero-field parameters. The parent compound exhibits a broad maximum around 34 K characteristic of a dimer with antiferromagnetic coupling that fit the Van Vleck susceptibility model well. It was found that the maxima could be tuned from 34 to 80 K by ligand substitution of the waters. Each compound possesses a characteristic color spanning the range of teal to pink. The g-value of each compound was found to be ∼1.98 using spectral simulation. The DMSO derivative is water soluble and has a high LC₅₀ for PC3 cancer cells, suggesting its use as a magnetic resonance imaging agent. X-ray crystal structure of the DMSO derivative [Cr₂(μ-oxo)₂(μ_1,2-C₄O₄)₂(C₂H₆SO)₄]·2H₂O (II) revealed that the DMSO ligands are equatorial, and the squarate groups bridge the two chromiums. This is in contrast to the previously proposed structure of the parent compound where the water ligands were axial and the equatorial squarate groups did not bridge the chromiums. These compounds are interesting because of their ease of synthesis, and their wide range of magnetic behavior. The compounds are good probes into antiferromagnetic dimer exchange by controlling the ligand field surrounding the superexchange pathway present in the molecule.