Abstract
Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al2O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al2O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O2 chemistry in air.
Highlights
Identification of chemical intermediates and the study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser material interactions but present challenges
Both optical spectroscopy and mass spectrometry (MS) analytical methodologies have been used for studies of chemistry in laser-induced vapors, such as infrared (IR) spectroscopy [1], molecular emission spectroscopy (MES) [2], time-resolved mass spectroscopy (TRMS) [3,4,5], and inductively coupled plasma-mass spectrometry (ICP-MS) [6]
One advantage of resonance fluorescence excitation of molecules is that a small gate width, down to a few nanoseconds, could be used to acquire high-quality spectra for analyses, which would significantly improve the temporal resolution of this technique and make it promising for chemical reaction analyses
Summary
Identification of chemical intermediates and the study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser material interactions but present challenges. One advantage of resonance fluorescence excitation of molecules is that a small gate width, down to a few nanoseconds (ns), could be used to acquire high-quality spectra for analyses, which would significantly improve the temporal resolution of this technique and make it promising for chemical reaction analyses. We chose aluminum (Al) as a sample for studying the temporal evolution of two important chemical intermediates, aluminum monoxide (AlO) and dialuminum monoxide (Al2O), in the Al-O2 chemistry This approach can be extended to other diatomic and polyatomic molecules. Benefits of this approach are rapid molecule identification (which is complementary to LIBS), temporal evolution monitoring of diatomic and polyatomic molecules as a potential tool for chemical reaction pathways and mechanisms analyses, and significantly improved temporal resolution for chemical reaction analyses with gate widths for detection down to a few nanoseconds
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