Abstract:Coincidence detection is of interest to get as much information as possible about transient events occurring in laser induced plasmas. The present work is focused on coincidence ion-photon detection of laser plasmas of high-energy organic compounds (TNT and DNT) in a condensed phase irradiated with UV laser pulses using an advanced instrument for simultaneous monitoring of both types of chemical species generated. The optical emission spectrum is acquired from atoms, atomic ions and diatomic molecules, whereas… Show more
“…Furthermore, there may be other species in the ejected plume for which spectral features are not observed, but whose presence can be confirmed through complementary techniques. 14,15 Several circumstances may cause such features to go undetected: insufficient energy transfer to excite the species, an extremely low concentration of the species, emission wavelengths outside the effective spectral measurement range, and/or emission lifetime outside the effective temporal measurement range. In any case, all species (even those not detected) can be involved in competing reaction pathways to form new species.…”
Section: Excited Matter: From Prompt To New Species Through Transientmentioning
Optical emission of laser-produced plasmas from solids, liquids, and gases, from their fundamentals to their potential applications, has been comprehensively reported in multiple research manuscripts, reviews, and books. There are nevertheless enough serious unanswered issues and questions still present on what at first sight seemed to be much easier, the laser-induced breakdown spectroscopy (LIBS) of organic compounds. Ideally, for all organic molecules, one would expect homologous emission spectra, differing only in the presence or absence of signals associated to the containing elements and their intensity relative to their content. Yet, the reality is much more complex. In laser-induced plasmas of organic compounds, a broad variety of species may be formed depending on the irradiation parameters. Furthermore, there is not a uniform breakage for all the molecules constituting the ablated mass. At once, the plasma is a dynamic entity per se, which implies that the spatial distribution of each species in the source plasma is different. In addition, multiple circumstances and mechanisms may contribute to the extinction of some species and the formation of new ones. Thus, the surrounding atmosphere where the plasma evolves and the time elapsed from its formation also have a strong influence on the spectral signature gathered. In essence, any change in any of the variables involved in the cycle of an organic plasma, from those causing its formation to those governing its expansion, defines a new scenario that lead to a different LIBS spectrum for a same organic compound. The present paper reviews the common emitting species populating the laser plasmas of organic compounds, the routes to their formation, mostly those related to the production of diatomic radicals, the dynamics of such species, in space and time, and the physical parameters that they confer to the plasma. Concurrently, the influence that the structures of the molecular solids and the set of excitation variables may exert on the optical emissions observed is also discussed. Finally, some details on the modeling of organic plasmas are provided.
“…Furthermore, there may be other species in the ejected plume for which spectral features are not observed, but whose presence can be confirmed through complementary techniques. 14,15 Several circumstances may cause such features to go undetected: insufficient energy transfer to excite the species, an extremely low concentration of the species, emission wavelengths outside the effective spectral measurement range, and/or emission lifetime outside the effective temporal measurement range. In any case, all species (even those not detected) can be involved in competing reaction pathways to form new species.…”
Section: Excited Matter: From Prompt To New Species Through Transientmentioning
Optical emission of laser-produced plasmas from solids, liquids, and gases, from their fundamentals to their potential applications, has been comprehensively reported in multiple research manuscripts, reviews, and books. There are nevertheless enough serious unanswered issues and questions still present on what at first sight seemed to be much easier, the laser-induced breakdown spectroscopy (LIBS) of organic compounds. Ideally, for all organic molecules, one would expect homologous emission spectra, differing only in the presence or absence of signals associated to the containing elements and their intensity relative to their content. Yet, the reality is much more complex. In laser-induced plasmas of organic compounds, a broad variety of species may be formed depending on the irradiation parameters. Furthermore, there is not a uniform breakage for all the molecules constituting the ablated mass. At once, the plasma is a dynamic entity per se, which implies that the spatial distribution of each species in the source plasma is different. In addition, multiple circumstances and mechanisms may contribute to the extinction of some species and the formation of new ones. Thus, the surrounding atmosphere where the plasma evolves and the time elapsed from its formation also have a strong influence on the spectral signature gathered. In essence, any change in any of the variables involved in the cycle of an organic plasma, from those causing its formation to those governing its expansion, defines a new scenario that lead to a different LIBS spectrum for a same organic compound. The present paper reviews the common emitting species populating the laser plasmas of organic compounds, the routes to their formation, mostly those related to the production of diatomic radicals, the dynamics of such species, in space and time, and the physical parameters that they confer to the plasma. Concurrently, the influence that the structures of the molecular solids and the set of excitation variables may exert on the optical emissions observed is also discussed. Finally, some details on the modeling of organic plasmas are provided.
“…Specific excitation conditions allow for simultaneous ion-photon detection ( Figure 12) although at expense of sacrificing the spectral performance. 61,62 Under tailored conditions, it is possible to perform LIMS and LIBS in a paired-shot scheme with two different fluence conditions optimized for each detection mode. As with Raman-LIBS, the sample entity is preserved using a first laser shot well below the plasma formation threshold to induce sample ionization, while the second pulse hits the sample on the same position at a larger fluence, allowing the recording of a LIBS spectrum under high vacuum conditions.…”
Section: Fusion With Libsmentioning
confidence: 99%
“…Specific excitation conditions allow for simultaneous ion–photon detection (Figure 12) although at expense of sacrificing the spectral performance. 61,62 Figure 12.Single-shot spectra of DNT recorded in a pulse-paired fashion using a first low-fluence pulse to record the mass spectra, followed by a second pulse at larger energy for the LIBS spectra. Both spectra were recorded in vacuum at 10 –6 mbar with 266 nm excitation.…”
“…During the LIBS measurement process, the plasma spectrum contains spectral characteristics of atom, iron, and molecule fragments, but we only used the atomic spectral line in this study. For certain specific measurements, the spectral characteristics of molecular fragments can be observed and used to directly image the molecular distributions [41,46,47,48]. Theoretically, LIBS can measure nearly all elements, but it is a problem for elements that exist in air, e.g., C, H, and O.…”
Sensing and mapping element distributions in plant tissues and its growth environment has great significance for understanding the uptake, transport, and accumulation of nutrients and harmful elements in plants, as well as for understanding interactions between plants and the environment. In this study, we developed a 3-dimensional elemental mapping system based on laser-induced breakdown spectroscopy that can be deployed in- field to directly measure the distribution of multiple elements in living plants as well as in the soil. Mapping is performed by a fast scanning laser, which ablates a micro volume of a sample to form a plasma. The presence and concentration of specific elements are calculated using the atomic, ionic, and molecular spectral characteristics of the plasma emission spectra. Furthermore, we mapped the pesticide residues in maize leaves after spraying to demonstrate the capacity of this method for trace elemental mapping. We also used the system to quantitatively detect the element concentrations in soil, which can be used to further understand the element transport between plants and soil. We demonstrate that this method has great potential for elemental mapping in plant tissues and soil with the advantages of 3-dimensional and multi-elemental mapping, in situ and in vivo measurement, flexible use, and low cost.
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