Measurement and Modeling of Ozone and Nitrogen Oxides Produced by Laser Breakdown in Oxygen—Nitrogen Atmospheres

Abstract

The production of ozone and nitrogen oxides was studied during multiple laser breakdown in oxygen–nitrogen mixtures at atmospheric pressure. About 2000 laser shots at 10¹⁰ W cm⁻² were delivered into a sealed reaction chamber. The chamber with a long capillary was designed to measure absorption of O₃, NO, and NO₂ as a function of the number of laser shots. The light source for absorption measurements was the continuum radiation emitted by the plasma during the first 0.2 μs of its evolution. A kinetic model was developed that encompassed the principal chemical reactions between the major atmospheric components and the products of laser breakdown. In the model, the laser plasma was treated as a source of nitric oxide and atomic oxygen, whose rates of production were calculated using measured absorption by NO, NO₂, and O₃. The calculated concentration profiles for NO, NO₂, and O₃ were in good agreement with measured profiles over a time scale of 0–200 s. The steady-state concentration of ozone was measured in a flow cell in air. For a single breakdown in air, the estimated steady-state yield of ozone was 2 × 10¹² molecules, which agreed with the model prediction. This study can be of importance for general understanding of laser plasma chemistry and for elucidating the nature of spectral interferences and matrix effects that may take place in applied spectrochemical analysis.