Measurement of Plasma Parameters in Laser-Induced Breakdown Spectroscopy Using Si-Lines

Abstract

The electron density and temperature of the laser induced silicon plasma were measured using two different methods. The plasma was produced via the interaction of high peak power Nd-YAG laser at the fundamental wavelength of 1064 nm with a plane solid iron target contain small traces of silicon as an element of minor concentration. The lines from the Si I at 288.15 nm and Si II-ionic lines at 413.08 and 634.71 nm were utilized to evaluate the plasma parameters. The reference plasma parameters were measured utilizing the Hα-line at 656.27 nm appeared in the spectra under the same condition. The electron density was measured utilizing the Stark broadening of the silicon lines and the temperature from the standard Saha-Boltzmann plot method. The comparison between electron densities from different silicon lines to that from the Hα-line reveals that the Si I-line at 288.15 nm contain some optical thickness while the Si II-ionic lines were found to be free from this effect. The measurements were repeated at different delay times between the laser and the camera in the range from 1 - 5 μsec. The electron density was found decreases from 2 × 10<sup>18</sup> down to 4 × 10<sup>17</sup> cm<sup>–3</sup>. After correcting the spectral intensity at the Si I-line at 288.15 nm, the temperatures evaluated from the different methods were found in an excellent agreement and decreases from 1.25 down to 0.95 eV with delay time

On the use of laser induced breakdown spectroscopy to characterize the naturally existing crystal in Pakistan and its optical emission spectrum

“…The ratio of the intensities of the lines is in accordance with the ratio of their statistical weights, an indication of an optically thin plasma. The Stark Broadening impact parameter is known only for the 634.89 line as 0.09 nm [20], after subtracting the instrumental width from the FWHM the corresponding electron density has been calculated as (0.97 ± 0.19) × 10 17 cm − 3 which is in good agreement with that deduced from the hydrogen Hα line.…”

“…At shorter wavelength, we have observed a triplet at 220.87 nm, 221.16 nm and 221.74 nm due to the 3s3p 3 3 D 1,2,3 → 3s 2 3p 2 3 P 0,1,2 transitions besides a line at 205.88 nm due to the 3s 2 3p5s 1 P 1 → 3s 2 3p 2 1 D 2 transition, at 212.47 due to 3s 2 3p3d 1 F 3 → 3s 2 3p 2 1 D 2 transition and a line at 230.38 nm due to the 3s 2 3p4d 1 P 1 → 3s 2 3p 2 1 S 0 transition. El Sherbini and Al Aamer [20] used the Si II line at 413 nm in the Saha-Boltzmann plot in determining the number density. The line profile is a close lying doublet, 3s 2 4f 2 F 5/2,7/2 → 3s 2 3d 2 D 3/2,5/2 , separated by about 0.02 nm, at 412.93 and 413.21 nm respectively.…”

“…), and Si II line at 505.60 nm (1.23 × 10 17 cm −3 ). El Sherbini and Al Aamer[20] determined the electron densities from the Hα line at 656.28 nm, Si I line at 288.15 nm, Si II lines at 413.08 and 634.71 nm and inferred that the densities calculated from the Si ionic lines are very close to that determined from the Hα line whereas that determined from the silicon line at 288.15 nm is higher which was stated that this line might be suffering from some optical thickness.…”

“…Khaleeq-ur-Rahman et al [17] captured the images of the time-integrated silicon plasma produced by a Nd:YAG (1064 nm) laser and studied shot-to-shot variation in the emission signal. The effect of ambient pressure on the laser induced silicon plasma temperature, density and its morphology has been studied by Cowpe et al [18,19] using a 532 nm Nd:YAG laser and reported the electron densities in the range 2.79 × 10 16 to 5.59 × 10 19 cm −3 and excitation temperatures of 9000-21,000 K. Recently, El Sherbini and Al Aamer [20] reported the plasma parameters from the emission lines of the laser produced silicon plasma and also reported, using double laser pulses of same energy, a signal enhancement by a factor of about 30 for the neutral silicon line at 288.16 nm and 100 for the doubly charged aluminum line at 281.62 nm. The electron density in the range of 4 × 10 17 -2 × 10 18 cm −3 and the plasma temperature in the range of 0.95 eV-1.25 eV were reported.…”

Laser induced damage studies in borosilicate glass using nanosecond and sub nanosecond pulses

“…The plasma formed during high power laser irradiation contains atoms and ions in different excited states, free electrons and radiation.The analysis of this plasma can be done through the measurement of plasma temperature (T e ) and free electron density (n e ). The plasma temperature describes the plasma state and the freeelectron density determines the thermodynamic equilibrium state of the plasma [25], [26].The knowledge of the plasma temperature and density of the plasma species is important for understanding the atomic ionization and excitationprocesses occurring inside the plasma. The emitted spectrum is shown in figure 8.…”