Atoms short pulse generation

Experimental lifetime measurements on free atoms and ions performed by using pulsed laser excitation in the ultraviolet and vacuum-ultraviolet spectral regions are presented. Different methods of laser pulse generation, atomization and light detection are described. A short summary of results obtained is also given. Future possibilities in determination of lifetimes and transition probabilities in the short wavelengths region are discussed. 

Background correction is thus achieved by modulating the lamp current to generate a longer pulse at low current (e. g. 9 ms at 5—10 mA), followed directly by a short pulse at high lamp current (for example, 0.3 ms at 200—300 mA). As the atom cloud persists in the hollow cathode lamp for several milliseconds, a minimum pulse repetition time of typically 50 ms is required to allow the atom cloud to clear before the next measurement cycle is started. 

This method is a radiation-chemical analog of pulse photolysis. High-performance spectrophotometry is used for the identification of particle detection. The kinetic information is processed by a computer. Active particles are generated by the electron impact with a short pulse of high-energy electrons, which induce the ionization and electron excitation of molecules, and excited molecules dissociate to form radicals and atoms. 

In the variety of excitation or de-excitation processes that allow the preparation and/or observation of the system via the participation of the continuous spectrum, the dominant and most interesting characteristics are generated by the transient formation of nonstationary or unstable states. For example, the excitation may be caused by the absorption of one or of many photons during the interaction of an initial atomic or molecular state with pulses of long or of short duration. Or, the transient formation and influence on the observable quantity may occur during the course of electron-atom scattering or of chemical reactions. 

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