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LIBS is a recently developed and rapid spectrochemical analysis technique and used to measure the relative elemental concentrations and their distribution within the samples [3, 5,15–18]. The schematic diagram of LIBS is shown in Figure 1.3. LIBS uses a high‐power pulsed laser beam that atomizes as well as excites the sample material. The creation of plasma happens only when the concentrated laser beam passes a threshold of power for an optical breakdown that is dependent of the target material and environment. LIBS can analyze any matter, be it solid, liquid or gas. Since all elements emit light of characteristic frequencies when excited to high temperatures, LIBS can detect all elements. It is limited by the power of the laser, sensitivity of the instrument, wavelengths corresponding to the spectrograph, and the detector. LIBS can be employed for the determination of the relative amount of element constituents and even impurities present in the sample material if the composition of the material is already known. Practically, it has been observed that the detection limits depend upon the temperature corresponding to the plasma excitation, the window used for the collection of light, and the line strength for the observed transitions.

LIBS is more advantageous for depth analysis due to its refocused capability on the same location of a sample surface and its ability to provide depth profiling at a resolution of hundreds of nanometers per pass. In addition, the laser beam can be focused from 20 to 200 μm and thus allows the laser beam to scan across the whole sample surface that provides spatially resolved elemental mapping. It can detect nearly all the naturally occurring element down to down to ppm level, depending on the sample matrix.

Figure 1.3 A schematic setup of laser‐induced breakdown spectroscopy (LIBS).

LIBS can even detect halogen‐based agents. The detection of heavy and toxic elements such as lead (Pb) and mercury (Hg) in soil and plants can be determined by employing a field‐portable LIBS system. It has been observed that the analysis of the spectral emission of aluminum and aluminum oxides arises from the bulk aluminum in distinct bath gases can also be possible. It is used for kinetic modeling of LIBS plumes. It is also used to detect and discriminate various materials belonging to the category of explosives, geological, plastics, landmines, chemical as well as biological warfare agents.

LIBS and XRF alike are generally used for positive material identification (PMI). For most of the applications, LIBS provides the same information as XRF, just using a laser source instead of radiation. But, in certain circumstances, one is better to use over the other. For example, handheld XRF systems are easy to use compared with handheld LIBS systems [3, 5]. Handheld XRF gives more precise results as compared with its LIBS counterpart. XRF is better than LIBS for the trace detection of elements below 0.1%. XRF can detect some heavier elements easily as compared to LIBS such as tungsten (W) which LIBS cannot vaporize. Handheld XRF is useful for testing a wider variety of elements however, LIBS is more suitable for the testing of lighter elements (C, H, N, O, B, and Li). Handheld LIBS is faster than XRF at testing. Also, the cost of a handheld XRF device is less than handheld LIBS.

Technically, the LIBS method is quite similar to other laser‐based analytical methods, where most of the hardware setup is same. LIBS can also be combined with Raman spectroscopy, and fluorescence (Laser induced fluorescence : LIF) [3, 5, 19]. Now‐a‐days, the manufactured devices combine these techniques in a single instrument, thereby allowing the atomic, molecular and structural characterization of a specimen, thus giving a deeper insight into the physical properties of it.