Differential excitation cross sections have been measured for Kr 4p ('So)~4p'( Pl/2 3/2)5s transitions at 300and 500-eV impact energies and for 1. 5'-10' scattering angles by electron-energy-loss spectroscopy. The integrated cross sections for these impact energies are reported here. The generalized oscillator strengths have also been obtained to determine the optical oscillator strengths.The errors are estimated to be less than 15%.

Absolute differential cross sections for the 3p 'S0~3p'('P, /2)4s, ('P3/2)4s excitation in argon have been measured at impact energies of 400 and 500 eV, and at scattering angles between 1. 75' and 10. 3' by electron-energy-loss spectroscopy. The integrated cross sections and generalized oscillator strengths (GOS's) have also been determined at 400 and 500 eV. The optical oscillator strengths have been determined, by extrapolating the GOS's to zero momentum transfer, as 0.222+0'03 for the ( Pl/2)4s state and 0.058+0008 for the ('P3/2)4s state. These data are compared with the results of other optical measurements in the vacuum-ultraviolet region. The errors are estimated to be less than 14%.

Basic characteristics of a particle detection method using laser breakdown were studied for a system of polystyrene standard particles dispersed in ultrapure water. The method was able to detect 0.02 µm particles. The detection sensitivity decreased with the particle size due to size dependence of the laser breakdown threshold. The plasma emission delay time from the laser pulse decreased with particle size (9.8±0.8 ns for 0.04 µm, 5.7±0.8 ns for 3.0 µm). The above results suggested the possibility of concentration and size measurement of fine particles in liquids by the proposed method.

Plasma emission delay time and plasma emission intensity of laser breakdown induced by a polystyrene particle in water were measured simultaneously. Short plasma emission delay time tended to correspond to high plasma emission intensity, as expected from the spatial and temporal profiles of the laser pulse power density. Particle size dependence of the correlation between the two parameters may serve in the measurement of the particle size.

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