Q-switched laser radiation at wavelengths of 355, 532, and 1064 nm from a Nd: YAG laser was used to generate plasma in laboratory air at the target surface made of nano-silver particles of size 95 ± 10 nm. The emitted resonance spectra from the neutral silver at wavelengths of 327.9 nm and 338.2 nm indicate existence of self-reversal in addition to plasma self-absorption. Both lines were identified in emission spectra at different laser irradiation wavelengths with characteristic dips at the un-shifted central wavelengths. These dips are usually associated with self-reversal. Under similar conditions, plasmas at the corresponding bulk silver target were generated. The recorded emission spectra were compared to those obtained from the nano-material target. The comparisons confirm existence of self-reversal of resonance lines that emerge from plasmas produced at nano-material targets. This work suggests a method for recovery of the spectral line shapes and discusses practical examples. In addition, subsidiary calibration efforts that utilize the Balmer series Hα-line reveal that other Ag I lines at 827.35 nm and 768.7 nm are optically thin under variety of experimental conditions and are well-suited as reference lines for measurement of the laser plasma electron density.

Enhanced emission from nano coated titanium target over than that from normal solid one was measured. The plasma was induced from both targets by the interaction of Nd: YAG laser source at a wavelength of 1064 nm. The enhanced signal emission was monitored using the Ti I-spectral lines at 453.32 and 498.17 nm. Another experiment was conducted after addition of a thin layer of 20 nm gold nanoparticles to the surface of bulk titanium. Enhancement factors were found up to twenty folds. The plasma-enhanced emission was attributed to the strong reduction in the plasma ignition threshold by a factor of 40 after adding the layer ofgold nanoparticles. Modeling to explain the origin of the strong reduction to the ignition threshold and enhanced emission is in advance which recommended that there a strong reduction of the thermal diffusion length of the bulk material to the limits of nanomaterial diameter size.

Detection of material ingredients is the main goal of the Laser-Induced Breakdown Spectroscopy (LIBS) technique. However, the light signal from the very little elemental concentration is small enough to produce large errors (relatively large limit of detection LOD). In order to enhance the light signal (spectral radiance) from the very small impurity concentrations, we suggested the addition of drops of gold nanoparticles (NPs) solution on the surface of metallic titanium in what is called nanoparticle-enhanced laser induced breakdown spectroscopy (NELIBS). The radiation from Nd:YAG pulsed laser at 1064 nm was used to irradiate the surface of titanium before and after the addition of nano-gold layer at an energy range from 60 mJ to 200 mJ in an open air. An echelle type spectrograph equipped with time controlled ICCD camera was used to resolve the emission spectrum from plasma. Ti I spectral lines at wavelengths of 453.32 and 498.17 nm were identified with recorded enhancement factors up to ×20, and this was achieved at the lower laser fluence of 4 J/cm 2. Strong reduction in the plasma ignition threshold by factor of 40 from the pure bulk titanium to nano-gold coated titanium was achieved, with similar reduction of limit of detection LOD. A theoretical work is in advance to explain the origin of the enhanced emission.