Abstract:
The experimental parameters optimal for studying the distribution of calcium atoms in laser-induced plasma at reduced pressure (16 Torr) by atomic fluorescence are determined. For the excitation and observation of fluorescence, a non-resonant fluorescence scheme was first proposed and implemented using transitions between states $4s4p(^3P^{\mathrm{o}})-4p^2(^3P)$ with wavelengths of 428.30 and 430.25 nm, respectively. Based on the analysis of the effect of target burnout on the fluorescence signal intensity and comparison of fluorescence saturation curves, it is shown that it is preferable to use a target made of pure calcium carbonate to observe fluorescence. A significant (62-fold) signal amplification when observing fluorescence under optimal conditions makes it possible to neglect the contribution of spontaneous emission to the intensity of the lines. A small effect of temperature within the limits observed in the diagnosed laser plasma on the population of the level used to excite fluorescence is also shown. After optimizing the parameters, this made it possible to carry out measurements with spatial resolution and establish the nature of the distribution of calcium atoms in the plasma along its lateral coordinate.
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