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Study of analyte dissociation and diffusion in laser-induced plasmas: implications for laser-induced breakdown spectroscopy

  • Plasma–particle interactions are explored through the introduction of single microdroplets into laser-induced plasmas. Both spectroscopic analysis and direct imaging of analyte atomic emission are used to provide insight into the various fundamental processes, namely desolvation, atomization, and atomic diffusion. By doping the 50 µm droplets with Lu, Mg or Ca, the analyte excitation temperature and the ion-to-neutral emission ratio are explored as a function of plasma residence time following breakdown. The data suggest a change in the local plasma conditions about the analyte atoms around 15–20 µs following breakdown, which may be interpreted as an overall transition from localized (i.e. perturbed) plasma conditions to the global (i.e. bulk) plasma conditions. A direct assessment of the hydrogen atomic diffusion coefficient following analyte desolvation reveals a value of 1.7 m² s-1 in the first 250–500 ns. This value is in good overall agreement with a theoretical analysis and withPlasma–particle interactions are explored through the introduction of single microdroplets into laser-induced plasmas. Both spectroscopic analysis and direct imaging of analyte atomic emission are used to provide insight into the various fundamental processes, namely desolvation, atomization, and atomic diffusion. By doping the 50 µm droplets with Lu, Mg or Ca, the analyte excitation temperature and the ion-to-neutral emission ratio are explored as a function of plasma residence time following breakdown. The data suggest a change in the local plasma conditions about the analyte atoms around 15–20 µs following breakdown, which may be interpreted as an overall transition from localized (i.e. perturbed) plasma conditions to the global (i.e. bulk) plasma conditions. A direct assessment of the hydrogen atomic diffusion coefficient following analyte desolvation reveals a value of 1.7 m² s-1 in the first 250–500 ns. This value is in good overall agreement with a theoretical analysis and with an analytical treatment of a surface source of hydrogen atoms. In contrast, calcium emission is only observed beyond about 1 µs, with a diffusion coefficient at least an order of magnitude below the hydrogen value. The temporal H and Ca emission data suggest that water vaporizes first, leaving an ever increasing Ca analyte concentration until finally, with nearly all water desorbed, the Ca fraction is vaporized. Overall, the data support the conclusion that finite time-scales of heat and mass transfer play an important role in localized plasma perturbations in the vicinity of the analyte, which has important implications for the LIBS analyte signal.zeige mehrzeige weniger

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Metadaten
Autor*innen:P.K. Diwakar, S. Groh, Kay Niemax, D.W. Hahn
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Journal of analytical atomic spectrometry
Jahr der Erstveröffentlichung:2010
Verlag:Royal Society of Chemistry
Verlagsort:London
Jahrgang/Band:25
Ausgabe/Heft:12
Erste Seite:1921
Letzte Seite:1930
DOI:10.1039/c0ja00063a
ISSN:0267-9477
ISSN:1364-5544
Verfügbarkeit des Dokuments:Physisches Exemplar in der Bibliothek der BAM vorhanden ("Hardcopy Access")
Bibliotheksstandort:Sonderstandort: Publica-Schrank
Datum der Freischaltung:19.02.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:17.01.2011
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