Stark broadening measurements in plasmas produced by laser ablation of hydrogen containing compounds

Abstract

8th Euro-Mediterranean Symposium on Laser Induced Breakdown Spectroscopy (EMSLIBS), Linz, AUSTRIA, SEP 14-18, 2015International audienceWe present a method for the measurement of Stark broadening parameters of atomic and ionic spectral lines based on laser ablation of hydrogen containing compounds. Therefore, plume emission spectra, recorded with an echelle spectrometer coupled to a gated detector, were compared to the spectral radiance of a plasma in local thermal equilibrium. Producing material ablation with ultraviolet nanosecond laser pulses in argon at near atmospheric pressure, the recordings take advantage of the spatially uniform distributions of electron density and temperature within the ablated vapor. By changing the delay between laser pulse and detector gate, the electron density could be varied by more than two orders of magnitude while the temperature was altered in the range from 6,000 to 14,000 K. The Stark broadening parameters of transitions were derived from their simultaneous observation with the hydrogen Balmer alpha line. In addition, assuming a linear increase of Stark widths and shifts with electron density for non-hydrogenic lines, our measurements indicate a change of the Stark broadening-dependence of H-alpha over the considered electron density range. The presented results obtained for hydrated calcium sulfate (CaSO4 center dot 2H(2)O) can be extended to any kind of hydrogen containing compounds. (C) 2016 Elsevier B.V. All rights reserved

Evaluation of pressure in a plasma produced by laser ablation of steel

“…This explanation seems to be in contradiction to the expansion dynamics of LIBS plasmas predicted by computer-simulations that indicate a welldefined vapor-gas contact front for the investigated time interval until 1 µs [8]. Similar values of electron density and temperature were reported for delays of some microseconds under different experimental conditions [9,10,11,12]. The existence of equilibrium is often discussed, but the questions of pressure and/or vapor-mass interdiffusion were mostly ignored [13].…”

“…The laser-produced plasma being characterized by a strong variation of n e and a moderate variation of T , the disregard of the T -dependence of ∆λ S tark is expected to have a small influence on the calculated spectral line profiles [21,12]. Since the Stark broadening parameters were not known for most transitions, we measured them in a separate experiment [23,11]. The Stark shift is obtained from Eq.…”

Ideal radiation source for plasma spectroscopy generated by laser ablation

“…The spectroscopic data were taken from NIST and Kurucz databases [23,24]. Most of the Stark broadening parameters were not found in the literature and therefore measured in a separate experiment, assuming a linear dependence of Stark widths and shifts on electron density n e [25]. For the calculation of the LTE plasma composition, we refer to previous work [26,27].…”

Two-step procedure for trace element analysis in food via calibration-free laser-induced breakdown spectroscopy

“…The Doppler width is calculated according to plasma temperature and atomic mass. The Stark width of each spectral line is obtained using Stark broadening parameters w and assuming a linear dependence of the Stark width with the electron density [36,37].…”