Sensitive detection of iodine by low pressure and short pulse laser-induced breakdown spectroscopy (LIBS)

Abstract

In this study, Laser-Induced Breakdown Spectroscopy (LIBS) technology was applied to detect iodine, an essential element for human body. Iodine in buffer gases of N₂ and air was detected using nanosecond and picosecond breakdowns of CH₃I at reduced pressure. Compared with the conventional methods of iodine measurement, LIBS technology without sample preparation shows the merits of fast response, real-time detection and enhanced detection limit. The measurement results of iodine demonstrated that low-pressure LIBS is the favourable method for trace species measurement in analytical applications. The plasma generation processes of multi-photon ionization and electron impact ionization can be controlled by pressure and laser pulse width for the larger ionization and excitation processes of iodine, which was discussed by the intensity ratio of iodine emission at 183 nm to nitrogen emission at 174.3 nm. The detection limit of iodine measurement in N₂ was 60 ppb in nanosecond breakdown at 700 Pa. Iodine in air as the buffer gas was also detected using nanosecond and picosecond breakdowns to examine the effect of oxygen.