Effects of atmospheric aerosols on radiative transfer are mainly studied because of their role in climate change. Aerosols also affect some technological applications by deteriorating range performance of electro-optical systems. This study focuses on the aerosol-induced attenuation of infrared radiation along a horizontal path. Measured attenuation values are compared with modeled ones and an attempt is made to understand the differences. Similar measurements have been done earlier; however, those measurements have not usually contained any information about the prevailing aerosol size distributions. Both measured and modeled aerosol extinction coefficients are studied as a function of different weather parameters (visibility, relative humidity and temperature). Measured size distributions are also investigated and they are compared with the size distribution assumed in MODTRAN4. Because measurements and extinction calculations contain some error sources, e.g. instrument errors and errors in aerosol growth factors, whose magnitudes are not exactly known, the total uncertainty was difficult to assess. Despite the uncertainty in the measurements, differences between measured size distributions and model size distributions were found. It appears that weather parameters do not offer the most feasible input data to model the aerosol extinction. In addition, aerosol extinction coefficients calculated from the measured size distributions were much lower than the measured and modeled values. The continuation of aerosol attenuation measurements in the future is of vital importance to obtain enough data for the analysis. Moreover, the accuracy of the measuring equipments should be comprehensively assessed.

Valence-band photoemission measurements were performed on VC0.80, VN0.89, VF3, and VF2+x at various photon energies across V 2p absorption edges. While on-resonance spectra of VC0.80 and VN0.89 are dominated by V LVV Auger lines, strongly resonating structures in spectra of vanadium fluorides remain at constant binding energies, thus indicating a Fano-type resonance. Analysis of the data indicates the importance of strong metal 3d–anion 2p hybridization for the description of the electronic structure of early transition metal compounds.

The resonant photoemission of the valence band in the vicinity of 2p ionization thresholds has been studied in Ti metal. For the first time, the resonant profile of the valence band as a function of photon energy has been determined. Both the thresholds,2p3/2 and2p1/2, show a separate resonance reaching an intensive maximum about 3 eV above the excitation edge. The difference between the ionization thresholds and the maxima is much less than in the resonance due to the 3p-3d excitation. This indicates that the probability for shake-up losses simultaneously with the core excitation is much lower at the 2p threshold than at the 3p threshold. For the same reason the width of the resonance also remains narrow.

The electronic structure of the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface has been studied in detail at a sample temperature of 55 K with high-energy-resolution angle-resolved photoemission. The photoemission spectra show a previously undetected surface-state structure at \ensuremath{\approx}0.5 eV below the Fermi level that we assign to dangling-bond states located mainly to the adatoms near the corner holes of the $7\ifmmode\times\else\texttimes\fi{}7$ reconstruction. Detailed dispersion curves obtained at 55 K are presented for the three uppermost, dangling-bond derived, surface states. Surface sensitive Si $2p$ spectra obtained in this low-temperature study still show a comparatively broad line shape. Possible reasons for this are discussed.

We report on the performance of a grazing incidence spherical grating monochromator installed at MAX I and designed to cover the photon energy range from about 15–200 eV with high resolving power. It is intended mainly for angle-resolved photoemission work. Therefore, both refocusing optics, to obtain a small spot size at the sample, and a higher order light suppressor, to reduce the content of higher orders, have been incorporated in the design. The theoretically calculated energy resolution is presented and compared to the resolution obtained in photoabsorption measurements of gas-phase He, Ne, Kr, Xe, and N2. The possibility to reduce the influence of higher orders is illustrated by photoemission data collected on Si (1 0 0). The experimental results show that the monochromator fulfills the expected design goals.

We have studied the resonant photoemission of the valence band in V, Cr, Mn and Co transition metals using synchrotron radiation excitation near the 3p ionization thresholds. The effect of the 3p - 3d interaction reaches maximum strength in Cr and Mn. On the other hand, the contribution related to the atomic Fano resonance goes to a minimum in Mn and increases rapidly on moving to Co. This behaviour is also reflected in the values of the effective Coulomb hole - hole interaction which we have calculated from experimental spectra. Furthermore, we have investigated when the Auger transition appears in the vicinity of the 3p ionization thresholds. Our results reveal that V, Cr and Co do not show the so-called subthreshold Auger emission whereas it can possibly be observed in Mn. However, we attribute the unusual appearance of the Auger peak to the wide valence band of Mn rather than the 3p - 3d resonance.

The photoionization cross section of the titanium 3d band, including the contributions from direct photoemission and autoionization, has been measured using synchrotron radiation on a wide photon energy range (21 – 110 eV). Particularly, we have concentrated on the resonant behavior of the valence band near the 3p and 3s threshold in which the influence of autoionization appears as drastic fluctuations of a resonant profile. In addition, we have examined subthreshold Auger emission that should already occur below the threshold energy.

The partial photoionization cross section of the titanium 3d band has been measured using synchrotron radiation in a wide photon energy range (21–110eV). Our prime interest has been concentrated on the resonant behaviour of the valence band in the vicinity of the 3p and 3s thresholds in which the influence of autoionization appears as drastic fluctuations of a resonant profile. The resonance close to the 3s excitation edge has been interpreted to be primarily caused by the p-character of the unoccupied band and the Cooper minimum of the 3p core level. We have also considered in details the effects which may distort a measured profile. In addition, we have examined the subthreshold Auger emission that should already occur below the edge energy. However, our study does not support the existence of the subthreshold Auger phenomenon in titanium.

The sulfur and lead species formed on galena (PbS) surface at different electrochemical potentials in acetate buffer solution (pH 4.6) were investigated using surface sensitive synchrotron radiation excited photoelectron spectroscopy (SR-XPS). At +50 to +150 mV versus SHE a new, very weak, S 2p component was observed at binding energy of about 2.8 eV higher than that from PbS, indicating that restructuring of the surface, due to oxidation, starts in this potential region. At +250 mV metal polysulfides were observed on the surface. In addition to polysulfides, enrichment of copper, present as a minor element in bulk of the natural galena sample, was detected. Since the quantity of polysulfides on the surface was not sufficient enough to explain the observed increase in S:Pb ratio with potential, it is proposed that copper diffuses from the bulk of the sample filling the vacant sites formed in anodic dissolution of lead. Formation of a metal deficient surface, where the sulfur state remains unchanged, is also possible. Indication of metallic lead, formed in reduction of PbS at -550 mV, was found.The better surface sensitivity gained by using synchrotron excitation instead of a conventional X-ray tube with Mg or Al anode turned out to be essential when studying submonolayer coverages of sulfur species on a sulfide mineral.

The inverse photoemission spectra of lead sulphide have been investigated in the energy range 15 – 33 eV of normal incidence electrons. In addition the angle-resolved photoemission spectra have been studied using synchrotron radiation. The sample crystals have been cleaved in UHV and the crystal structure has been observed by LEED to correspond the (1×1) surface geometry. The band structure to the direction Γ - X has been determined below and above the Fermi-level from the photoemission and the inverse photoemission spectra. The prominent dispersion of one occupied band is clear but the others are markedly flat. The unoccupied bands show quite well behaving dispersion. There are no bands crossing the Fermi-level in the Γ - X direction displaying the band gap 3.6 eV. General shapes of the experimental band dispersions agree satisfactorily with those predicted by theoretical calculations, but the binding energies of the bands show clearly some disagreement, especially for the lowest bands.

The photoemission from vanadium has been studied by using synchrotron radiation in the photon energy range 36 – 130 eV. We report here our first results of vanadium. The resonance photoemission and a closely related Auger event has been observed. Furthermore the binding energies of 3s and 3p has been determined.