Low-divergence operation of a long-pulse excimer laser using a SBS phase-conjugate cavity

The use of an optical cavity containing a stimulated Brillouin scattering (SBS) phase-conjugate reflector to control the spatial and spectral output of a long pulse (>100 ns) X-ray preionized XeCl laser is reported. The divergence of the 3×4 cm² output beam has been improved by a factor of 20 to <150 rad. The temporal form of the output depends on the acoustic decay times of the liquid and gaseous SBS media used. Four-wave mixing via gain saturation has been observed within the discharge volume, leading to depolarisation of the output beam.     

New fluorinated hydroxamic acid reagents for the extraction of metal ions with supercritical CO2

Research to date on the supercritical fluid extraction (SFE) of metal ions has focused on the use of dithiocarbamates and β-diketones. Hydroxamic acids are well known as effective chelating agents for a broad range of transition metal ions. Much attention has centred in inorganic chemistry on the effect of N-substitution on metal chelate stability and selectivity, and in analytical chemistry on the immobilisation of the chelating agents to the chosen solid supports such as silica. In this paper, the synthesis of selected fluorinated mono hydroxamic acids and their N-substituted derivatives is reported. The new reagents are applied in the SFE of metal ions in particular Fe(III) using unmodified supercritical CO₂. Metal extraction is monitored using atomic absorption spectroscopy and visible spectrophotometry. The extraction efficiencies were determined as a function of pressure and temperature. The new ligands synthesised and applied were perfluorooctanohydroxamic acid (PFOHA), heptafluorobutyrichydroxamic acid (HFBHA) and their N-methylhydroxamic acid derivatives. Of the synthesised reagents, PFOHA was the most soluble and effective extractant of Fe(III) from spiked filter paper, reaching 97% extraction of the metal ion under optimised conditions. The selectivity of this ligand for Fe(III) in the presence of Cu(II), Ni(II), Pb(II) and Zn(II) is also demonstrated.     

Non-aqueous sers: Pyridine in N,N'-dimethylformamide solution at a silver electrode

Surface-enhanced Raman spectra are reported from pyridine in N,N′-dimethylformamide at a silver electrode. Potential and time-dependent results are presented and discussed in terms of the electrode surface morphology.     

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