The experimental findings obtained, particularly interesting for cultural heritage field-applications, show that lowering the irradiance, the average ablation rate decreases and depth of the crater becomes less. The effect of changing WD on the intersection point, the average ablation rate and the crater depth of Au and Ag thin films onto Cu substrates has been studied by using 50 mJ, Nd:YAG laser pulses. length of the lens, has been found to be a very critical parameter. Laser-induced breakdown spectroscopy (LIBS) is a relatively novel technique that is being applied to the characterization of interfaces in layered materials as an alternative to other classic surface analytical techniques.In the present work the change of laser irradiance (W/cm2) by changing the working distance (WD), which is the difference between the lens-to-sample distance and the focal. The first results obtained with remote filament-induced breakdown spectroscopy predict sample analysis at kilometer ranges. The high-power densities achievable with these laser pulses can also induce self-guided filaments in the atmosphere which produce LIBS excitation of a sample. Recent stand-off analyses of metal samples have been reported using femtosecond laser pulses to extend LIBS capabilities to very long distances. These different configurations have been used depending on the application such as rapid sorting of metal samples, identification of material in nuclear industry, process control and monitoring in metallurgical industry, applications in future planetary missions, detection of environmental contamination or cleaning of objects of cultural heritage. The light collection device can be either at an angle from the laser beam path or collinear with the optical axis of the system used to focus the laser pulses on the target surface. For stand-off LIBS analysis, a lens or a mirror is required to increase the solid angle over which the plasma light can be collected. Efficient collection of the plasma light is also needed to obtain analytically useful signals. A large variety of laser focusing systems have been employed for stand-off analysis comprising refracting or reflecting telescope. The distances achievable depend on many parameters including the laser characteristics (pulse energy and power, beam divergence, spatial profile) and the optical system used to focus the pulses at a distance. Liquid samples have also been analyzed at distances of a few meters. Open-path stand-off LIBS has mainly been used with nanosecond laser pulses for solid sample analysis at distances of tens of meters. It does not present the results obtained with a transportation of the laser pulses to the target through an optical fiber. returning plasma light are transmitted through the atmosphere. This review only refers to the use of the open-path LIBS configuration in which the laser beam and the. Stand-off LIBS was suggested for elemental analysis of materials located in environments where any physical access was not possible but optical access could be envisaged. A review of recent results on stand-off Laser-Induced Breakdown Spectroscopy (LIBS) analysis and applications is presented.
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