TY - JOUR
T1 - Investigation of polarization effects for nanosecond laser-induced breakdown spectroscopy
AU - Asgill, M. E.
AU - Moon, H. Y.
AU - Omenetto, N.
AU - Hahn, D. W.
N1 - Funding Information:
This work was supported by the National Science Foundation through grant CHE-0822469 , as part of the Plasma–Analyte Interaction Working Group (PAIWG), a collaborative effort of the University of Florida, Federal Institute of Materials Research and Testing (BAM) in Berlin, and ISAS at Technische Universität Dortmund, jointly funded by the NSF and DFG .
PY - 2010/12
Y1 - 2010/12
N2 - The spectral and temporal polarization dependencies of nanosecond laser-induced plasmas are explored for analysis of gaseous and solid samples using various experimental configurations. Plasma emission measurements were resolved into vertical and horizontal polarization components, and the ratio of the two polarization-resolved measurements was calculated for each sample and configuration. For the solid target, measurements were recorded with the sample oriented both normal to the incident laser beam as well as at oblique angles of incidence. The results for the breakdown of a pure, nitrogen gaseous sample revealed no degree of polarization in either the continuum or atomic emission, with the ratios of the horizontally-to-vertically resolved plasma emission showing values equal to unity when resolved both temporally and spectrally. The analysis of both copper and steel solid samples also showed no polarization dependency in the spectral and temporal data when the laser was incidentally normal to the sample surface. For oblique angles of incidence, some polarization (< 10%) was observed within the first tens of nanoseconds of plasma lifetime. The polarization was manifested as a slight reduction in the horizontal component of plasma emission, but significantly, the observed polarization was found to be spectrally flat, with no difference observed between continuum and atomic emission features. The small polarization effect was found to diminish with plasma residence time, effectively vanishing by about 1 μs following breakdown. The transient polarization is hypothesized to arise from reflection effects (i.e. Fresnel reflectivity) between the plasma light and the solid target surface present with oblique angles of incidence for reflected light, with temporal effects due to the dynamic nature of the plasma development and plasma-surface interactions. Overall, no evidence was found to support any inherent anisotropy or polarization specific to the plasma continuum or the atomic emission for the transitions studied.
AB - The spectral and temporal polarization dependencies of nanosecond laser-induced plasmas are explored for analysis of gaseous and solid samples using various experimental configurations. Plasma emission measurements were resolved into vertical and horizontal polarization components, and the ratio of the two polarization-resolved measurements was calculated for each sample and configuration. For the solid target, measurements were recorded with the sample oriented both normal to the incident laser beam as well as at oblique angles of incidence. The results for the breakdown of a pure, nitrogen gaseous sample revealed no degree of polarization in either the continuum or atomic emission, with the ratios of the horizontally-to-vertically resolved plasma emission showing values equal to unity when resolved both temporally and spectrally. The analysis of both copper and steel solid samples also showed no polarization dependency in the spectral and temporal data when the laser was incidentally normal to the sample surface. For oblique angles of incidence, some polarization (< 10%) was observed within the first tens of nanoseconds of plasma lifetime. The polarization was manifested as a slight reduction in the horizontal component of plasma emission, but significantly, the observed polarization was found to be spectrally flat, with no difference observed between continuum and atomic emission features. The small polarization effect was found to diminish with plasma residence time, effectively vanishing by about 1 μs following breakdown. The transient polarization is hypothesized to arise from reflection effects (i.e. Fresnel reflectivity) between the plasma light and the solid target surface present with oblique angles of incidence for reflected light, with temporal effects due to the dynamic nature of the plasma development and plasma-surface interactions. Overall, no evidence was found to support any inherent anisotropy or polarization specific to the plasma continuum or the atomic emission for the transitions studied.
KW - Fresnel reflectivity
KW - Gated detection
KW - Laser-induced breakdown spectroscopy
KW - Observation geometry
KW - Polarization
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U2 - 10.1016/j.sab.2010.11.010
DO - 10.1016/j.sab.2010.11.010
M3 - Article
AN - SCOPUS:78651341807
SN - 0584-8547
VL - 65
SP - 1033
EP - 1040
JO - Spectrochimica Acta - Part B Atomic Spectroscopy
JF - Spectrochimica Acta - Part B Atomic Spectroscopy
IS - 12
ER -