Plasma emission induced by an Nd-YAG laser at low pressure on solid organic sample, its mechanism, and analytical application

Abstract

An Nd-YAG laser (1064 nm, 120 mJ, 8 ns) was focused on various types of solid organic samples such as a black acrylic plate, a black polyvinyl chloride plastic sheet, and a methoxy polyaniline film coated on the surface of a glass substrate, under a surrounding air pressure of 2 Torr. A modulated plasma technique was used to study the mechanism of excitation of the emission of the organic material. As a result, we conclude that ablated atoms and molecules are excited by a shock-wave mechanism, similar to the case of hard samples such as metal. The ablation speed of hydrogen emission (H I 656.2 nm) was examined and the results show that the release speed of the ablated atoms is relatively low (less than Mach 10) and persists for a longer period of time (around 1 μs); this phenomenon can be understood by assuming that the soft target absorbs recoil energy, causing a low release speed of ablated atoms which would form the shock wave. This was overcome by placing a subtarget on the back of the soft sample so as to enhance the repelling force, thus increasing the release speed of the atoms. A possible application of the low-pressure plasma on an organic solid was demonstrated in the detection of chlorine in a black polyvinyl chloride plastic sheet.

Analytical Approach of Laser-Induced Breakdown Spectroscopy to Detect Elemental Profile of Medicinal Plants Leaves

“…The integration time and laser energy were fixed during the mesurements. The behavior of emission signals at low pressure has also explained by Suliyanti et al [2] by focusing Nd: YAG laser on different organic samples at low pressure using substrate behind the target. There are two distinct parts of plasma emission at low pressure, in primary part for short period there was continuum emission and in secondary part, there was a strong emission of atomic spectral lines in expanded plasma [2].…”

“…These techniques requires sample preparations and involve solutions during their analysis process which may contaminate them and affect the qualitative and quantitative results. Line profiles of essential nutrients of these plants have also discussed at different time delay, energy and ambient pressures [2][3][4][5]. The detection of CN band is important to analyze actual content of C and N with CN band emission by LIBS.…”

A Review of Development in the Research of Self-Absorption on Laser-Induced Breakdown Spectroscopy

“…For instance, Suliyanti et al 103 conducted a study on plasma emission induced from a solid organic analyte at low-pressure. They findings revealed that emission lines generated at lower gas pressure displayed more distinct profiles compared to those generated at higher-pressure This observation was attributed to the diminished ablation process that occurs at lower pressure.…”