Spectral characteristic of laser-induced plasma in soil

Abstract

The spectral characteristic of laser-induced plasma in soil was studied in this work, laser-induced breakdown spectroscopy was used to analyze the spectral characteristic of plasma under the condition of different time delays and irradiances. Moreover, the time evolution characteristics of plasma temperature and electron density were discussed. Within the time delay range of 0-5 μs, the spectral intensity of the characteristic lines of Si I: 288.158 nm, Ti I: 336.126 nm, Al I: 394.400 nm and Fe I: 438.354 nm of the four main elements in two kinds of national standard soil decayed exponentially with time. The average lifetime of the spectral lines was nearly 1.56 μs. Under the condition of different time delays, the spectral intensity of Pb I: 405.78 nm in soil increased linearly with laser energy. However, the slope between the spectral intensity and laser energy decreased exponentially with the increase in time delay, from 4.91 to 0.99 during 0-5 μs. The plasma temperature was calculated by the Boltzmann plot method and the electron density was obtained by inversion of the full width at half maximum of the spectrum. The plasma temperature decreased from 8900 K to 7800 K and the electron density decreased from 1.5×10 17 cm −3 to 7.8×10 16 cm −3 in the range of 0-5 μs.

Atomic spectrometry update – a review of advances in environmental analysis

“…A method for the measurement of non-metallic elements in herbal teas used 159 O 2 and H 2 sequentially as reaction gases. First, O 2 was introduced to the cell and Br, I, P and S measured as their oxide ions; then H 2 was introduced and Cl measured as H 2 35 Cl + and Si as 28 Improvements in the LIBS analysis of soil were achieved through study and optimisation of the laser energy, 165,166 pressure, 167 lens-to-sample distance 166 and time delay between irradiation and signal acquisition. [165][166][167] Application of a magnetic eld perpendicular to the plasma increased 168,169 plasma temperature and hence analyte emission intensities and thereby lowered LODs.…”

“…Improvements in the LIBS analysis of soil were achieved through study and optimisation of the laser energy, 165,166 pressure, 167 lens-to-sample distance 166 and time delay between irradiation and signal acquisition. 165–167 Application of a magnetic field perpendicular to the plasma increased 168,169 plasma temperature and hence analyte emission intensities and thereby lowered LODs. Spatial confinement of the plasma within a cylindrical cavity achieved 170 the same result.…”

Effect of DBD plasma excitation characteristics on turbulent separation over a hump model

“…Liu et al [10] studied the effect of excitation voltage on the separation flow under steady plasma excitation using this model. Yu et al [11] applied numerical simulations to study the effect of unsteady excitation and plasma excitation voltage on the separation of the same hump model.…”

“…Zhang et al [17] employed it to study the flow structures of the boundary layer in a flat plate induced by a plasma actuator. Yu et al [11] used the linear body approach and found that the vortex pairs, which are reduced by a plasma, would enhance the energy exchanged between the near wall region and the free stream. In the present work, the phenomenological body force approach proposed by Shyy et al [12] will be adopted.…”

“…The essence of the plasma's normal excitation is a kind of wall jet [18]; the pulsed excitation is to intermittently turn on or off the plasma excitation. The influence of excitation intensity of conventional excitation on the separation of the hump model has been thoroughly studied [10,11]. Current research on the unsteady excitation of plasma over a negative pressure gradient focuses on the comparison with the steadystate control, and these studies [7,8,10,11] only used one fixed excitation frequency and duty cycle.…”