Plasma Dynamics in Double-Pulse LIBS on Dicarboxylic Acids Using Combined 532 nm Nd:YAG and Carbon Dioxide Laser Pulses

Abstract

Laser-induced breakdown spectroscopy (LIBS) was used as a method to monitor the evolution of C, hydrogen-α, carbon–carbon, and carbon–nitrogen spectral emissions from atmospheric recombination in a specific set of organic materials. Ablated samples were composed of a series of linear chain dicarboxylic acids with two to seven C atoms. Accumulated pulses of a focused neodymium-doped yttrium aluminum garnet (Nd:YAG) Q-switched laser beam operated at 532 nm generate a plasma in air at the sample surface. In this work, a dual-pulse LIBS technique was used to improve signal strength by enhancing the nanosecond LIBS plasma with CO₂ transverse-excited breakdown in atmosphere laser pulses with an operating wavelength of 10.6 μm. Through a time-resolved analysis, we demonstrate the correlation between the signal strength of selected emissions and the number of C atoms in the linear chain. We also illustrate the effects that these constraints, along with the presence of a chiral C in the chain, have on the peak intensities of the individual lines with respect to each other by comparing the increase or nonexistence of certain spectral lines as we increase the number of C atoms in the linear chain.