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Following positive laboratory-scale experiments, we investigated the ability to trigger real-scale lightning using ionized filaments generated by ultrashort laser pulses in the atmosphere. Under thunderstorm conditions, we observed electric events synchronized with the laser pulses.

The deflection of a sodium atomic beam by the radiation pressure of the light of a cw dye laser was investigated. From the deflection observed it is deduced that the linear momentum trasferred corresponds to an average of 60 excitations per atom. The linewidth of the dye laser used for the measurements was smaller than 50 MHz.

Molecules whose electronic transitions lie in the UV portion of the electromagnetic spectrum far outnumber those in the visible. Consequently, it is of considerable chemical interest to extend tunable coherent light sources to shorter wavelengths. Potential applications are numerous including photo-chemical, kinetic, analytical and spectroscopic studies. Because dye lasers are limited to wavelengths above 330 nm, the production of deeper UV light requires the use of non linear optics such as sum frequency mixing and harmonic generation1.

Molecules whose electronic transitions lie in the UV portion of the electromagnetic spectrum far outnumber those in the visible. Consequently, it is of considerable chemical interest to extend tunable coherent sources to shorter wavelengths. Potential applications are numerous, including photochemical, kinetic, analytical, and spectroscopic studies. We report here the construction of an intracavity-doubled cw ring dye laser producing single-mode UV output in the range 250–260 nm with a free-running jitter of about ±50 MHz over a time interval of a few seconds. High resolution spectra of the Hg 3P1 - 1S0 transition at 253.7 nm are presented. Fluorescence excitation of natural mercury in a bulb yields a spectrum in which the resolution of the hyperfine structure is Doppler limited, whereas excitation of an atomic beam allows subDoppler resolution of these features.