[1] During the Lindenberg Aerosol Characterization Experiment (LACE 98) simultaneous measurements with ground-based and airborne lidars and with two aircraft equipped with aerosol in situ instrumentation were performed. From the lidar measurements, particle backscatter coefficients at up to eight wavelengths between 320 and 1064 nm and particle extinction coefficients at 2-3 wavelengths between 292 and 532 nm were determined. Thus, for the first time, an extensive set of optical particle properties from several lidar platforms was available for the inversion into particle microphysical quantities. For this purpose, two different inversion algorithms were used, which provide particle effective radius, volume, surface-area, and number concentrations, and complex refractive index. The single-scattering albedo follows from Mie-scattering calculations. The parameters were compared to the ones from airborne measurements of particle size distributions and absorption coefficients. Two measurement cases were selected. During the night of 9 -10 August 1998 measurements were taken in a biomass-burning aerosol layer in the free troposphere, which was characterized by a particle optical depth of about 0.1 at 550 nm. Excellent agreement between remote-sensing and in situ measurements was found. In the center of this plume the effective radius was approximately 0.25 m, and all methods showed rather high complex refractive indices, ranging from 1.56 -1.66 in real part and from 0.05-0.07i in imaginary part. The single-scattering albedo showed low values from 0.78 -0.83 at 532 nm. The second case, taken on 11 August 1998, presents the typical conditions of a polluted boundary layer in central Europe. Optical depth was 0.35 at 550 nm, and particle effective radii were 0.1-0.2 m. In contrast to the first case, imaginary parts of the refractive index were below 0.03i. Accordingly, the single-scattering albedo ranged from 0.87-0.95.

The dynamics of molecular multiphoton ionization and fragmentation of a diatomic molecule (Na2) have been studied in molecular beam experiments. Femtosecond laser pulses from an amplified colliding-pulse moddocked (CPM) ring dye laser are employed to induce and probe the molecular transitions. The final continuum states are analyzed by photoelectron spectroscopy, by ion mass spectrometry and by measuring the kinetic energy of the formed ionic fragments. Pumpprobe spectra employing 70-fs laser pulses have been measured to study the time dependence of molecular multiphoton ionization and fragmentation. The oscillatory structure of the transient spectra showing the dynamics on the femtosecond time scale can best be understood in terms of the motion of wave packets in bound molecular potentials. The transient Na2+ ionization and the transient Na+ fragmentation spectra show that contributions from direct photoionization of a singly excited electronic state and from excitation and autoionization of a bound doubly excited molecular state determine the time evolution of molecular multiphoton ionization.

and optical modeling, we investigate the possible evolution of this cloud assuming either in situ freezing of ternary HNOa/H2SO4/H20 droplets as nitric acid trihydrate, or the formation of the clouds in mountain waves over the east coast of Greenland, as suggested by a mountain wave model. Best agreement with the observations was obtained by assuming mountain-wave-induced cloud formation, which yields nitric acid trihydrate particles with much higher total mass than achieved by assuming synoptic-scale freezing. Our analysis suggests that this rare type of PSC, which we term type Ia-enh, is characterized by nitric acid hydrate particles rather close to thermodynamic equilibrium, while the more common type Ia PSCs appear to contain much less mass than representative of equilibrium.

Based on reliable, carefully selected data sets, equations for the thermal conductivity and the viscosity of the refrigerant R 152a are presented. They are valid at temperatures from 240 to 440 K, pressures up to 20 MPa, and densities up to 1050 kg. rn -s, including the critical region.

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