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Electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM) and photoacoustic spectroscopy (PAS) has been used to study the electronic structure of small Ag, In and Au particles, deposited on thin carbon foils, quartz supports or as self-supporting layers, respectively.In the low energy-loss region the EELS spectra of Ag particles with diameters of ca. 50 nm are different from the spectra of the homogeneous Ag layers, mainly owing to the influence of the carbon foil. By decreasing the packing density of the Ag particles, a shift of the plasma losses to lower energies is observed in the energy region 10 eV. The optical behaviour of homogeneous metallic and small particle layers on thin quartz supports was studied by PAS in the ultraviolet/visible (UV/VIS) spectral region. The homogeneous layers, e.g. of Ag, show, in the UV range, the well known change of reflectance due to an interband transition of bare silver. For Ag particle layers surface plasma resonances are excited. With increasing packing density of the particles the absorption peak observed is red-shifted and becomes broader, whereas the results of EELS in the low energy-loss region revealed a shift to higher energies.To obtain additional information investigations of In and Au particles were performed.

The performance of a novel portable, tunable diode laser, resonant photoacoustic (TDL-PA) analyzer developed for field measurements of CH4 was compared to a commonly applied offline gas chromatographic (GC) method. This comparative studywas realized under normal field conditions parallel to long-term weekly GC monitoring of four different soil types with very different methane budgets. The method used for gas-exchange measurements was the well-known closed-chamber technique. The TDL-PA analyzer detects methane at 1650.957 nm [R (5) line of the 2v3 band], guaranteeing high precision without the need for correction procedures. The two techniques correlated well (R2 = 0.988) over the entire concentration range (0.15-33 ppmv CH4) tested at highly varying flux rates between -30 and -12 ppbv CH4 min(-1) for uptakes and between 2.5 and 362 ppbv CH4 min(-1) for emissions. The two analyzers proved to be interchangeable, leaving the online advantages to the TDL-PA. A suitable CH4 online GC solution for chamber measurement is not available as a portable system. Additionally, the data sampling rate of 2 Hz enables a direct coupling to other infrared gas analyzers with the high time resolution commonly required to determine plant CO2 assimilation rates or soil respiration rates.

Photoacoustic spectrometry in the ultraviolet, visible and near-infrared regions was employed to study the absorption behaviour of the colourant annatto and to determine its content in commercial seasoning products via the intensity of an absorption peak compared with the absorption of standard samples with a known content of annatto. Owing to strong absorption and as a consequence saturation of the signal of the pigment in the ultraviolet and visible regions, a peak of weak absorption in the near-infrared region was used, guaranteeing a linear relationship between peak intensity and annatto content for the usually applied low to medium levels of dye contents in commercial products.