Surface enhanced absorption and transmission from dye coated gold nanoparticles in thin films.

Absorption spectra of gold nanoisland thin film and the composite film of gold having thin coating of Methylene Blue and Rh6G dyes have been studied. Thin gold nanoisland film shows surface plasmon resonance (SPR) peak in the visible wavelength range, which shifts to near infrared with an increase in the thickness of the film. It was found that thin film of gold consists of nanoparticles of different size and shape, particularly nanorods of noncylindrical shapes.

Theoretical model for double pulse laser-induced breakdown spectroscopy.

We present a simple theoretical model for the emission from double pulse laser-induced plasmas that was developed to better understand the processes and factors involved in enhancement of plasma emission. In this model, the plasma emission is directly proportional to the square of plasma density, its volume, and the fraction of second laser pulse absorbed through inverse bremsstrahlung absorption by the plasma plume of the first laser pulse. The electron-ion collision frequency determines the profile and location of the peak of emission enhancement with respect to the delay between the two lasers, whereas the amplitude of the enhancement is mainly dependent on the increase in the mass ablation rate after the second laser pulse.

Time-dependent single and double pulse laser-induced breakdown spectroscopy of chromium in liquid.

A study of aqueous solutions of chromium using single and double pulse laser-induced breakdown spectroscopy (LIBS) is presented. Three atomic emission lines show enhancement in emission under dual pulse LIBS excitation. The temporal evolution of line emission indicates that a shock wave front produced by the first laser pulse plays an important role in determining the decay rate of intensity by excitation transfer in single pulse LIBS and by plasma confinement in double pulse LIBS.

Effect of steady magnetic field on laser-induced breakdown spectroscopy.

Effects of a steady magnetic field on the laser-induced breakdown spectroscopy of certain elements (Mn, Mg, Cr, and Ti) in aqueous solution were studied, in which the plasma plume expanded across an external steady magnetic field (approximately 6 kilogauss). Nearly 1.6 times enhancement in the line emission intensity was observed in the presence of the magnetic field.

Study of laser-induced breakdown emission from liquid under double-pulse excitation.

The application of laser-induced breakdown spectroscopy to liquid samples, by use of a Nd:YAG laser in double-pulse excitation mode, is described. It is found that the line emission from a magnesium ion or atom is more than six times greater for double-pulse excitation than for single-pulse excitation. The effect of interpulse separation on the emission intensity of a magnesium ion and a neutral atom showed an optimum enhancement at a delay of 2.

Optical emission from laser-induced breakdown plasma of solid and liquid samples in the presence of a magnetic field.

The optical properties of laser-induced plasma generated firm solid (Al alloy) and liquid (Mn, Cr, Mg, or Ti solutions) samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy. Various line emissions obtained from the constituents of the Al alloy and of the aqueous solution show an enhancement in intensity in the presence of an approximately 5-kG magnetic field. The enhancement of the signal was nearly a factor of 2 for the minor constituents of the solid samples and a factor of 1.