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Use of NH (A3Π-X3Σ-) sonoluminescence for diagnostics of nonequilibrium plasma produced by multibubble cavitation

Abstract

In this work, sonoluminescence of NH radicals has been evaluated as a new spectroscopic probe for nonequilibrium plasma produced by multibubble cavitation in liquids. The experiments were performed in aqueous ammonia solutions submitted to power ultrasound at low and high frequency and under two different rare gases (Ar and Xe). Sonoluminescence (SL) spectroscopy focuses on the emission of the two present systems: NH (A3Π-X3Σ-) and OH (A2Σ+-X2Π). Both spectroscopic systems indicate the absence of thermal equilibrium during bubble collapse (Tv >Tr) whatever the saturating gas. When Ar is used as the saturating gas, these emissions can be fitted with Specair software and corresponding rovibronic temperatures are derived. Both species indicate a net increase in vibrational temperatures with the US frequency. In Xe, the SL spectra exhibit OH (C2Σ+-A2Σ+) and NH (c1Π-a1Δ) emission bands indicating higher electron temperature compared to Ar. However, in Xe the SL spectra of cannot be satisfactorily fitted because of significant line broadening. The estimation of the intrabubble pressure via simulation of SL with Specair software is discussed. Monitoring of the sonochemical activity indicates the formation of H2 and N2H4 while no H2O2 accumulates in these conditions. In the presence of Xe, NO is also formed as sonolysis product. The appearance of new possible reaction pathways under Xe is made possible by the higher plasma electron density and correlates with SL data.

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Publication details

The article was received on 17 Jul 2017, accepted on 05 Sep 2017 and first published on 05 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04813K
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Use of NH (A3Π-X3Σ-) sonoluminescence for diagnostics of nonequilibrium plasma produced by multibubble cavitation

    R. pflieger, O. Temim, T. Belmonte and S. Nikitenko, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04813K

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