Laser-induced breakdown spectroscopy of ammonia gas with resonant vibrational excitation

Guang Yang, Lei Liu, Tao Wang, Lisha Fan, Xi Huang, Di Tian, Lan Jiang, Jean François Silvain, Yongfeng Lu

Research output: Contribution to journalArticle

Abstract

In this work, laser-induced breakdown spectroscopy (LIBS) of gaseous ammonia (NH3) molecules on- and off-resonant vibrational excitation was studied in open air. A wavelength-tunable, continuous wave (CW), carbon dioxide (CO2) laser tuned at a resonant absorption peak (9.219 µm) within the infrared radiation (IR) range was used to resonantly excite the vibration of the N-H wagging mode of ammonia molecules. A pulsed Nd:YAG laser (1064 nm, 15 ns) was used to break down the ammonia gas for plasma imaging and spectral measurements. In this study, plasmas generated with the ammonia molecules without additional CO2 laser beam irradiation and with additional CO2 laser beam irradiation with the wavelengths on- and off-resonant vibrational excitation of ammonia molecules were investigated and referred as LIBS, LIBS-RE-ON and LIBS-RE-OFF, respectively. The experimental results showed that the temporal and spatial evolution as well as electron temperature and density of plasmas induced with LIBS and LIBS-RE-OFF were consistent but differed from LIBS-RE-ON. Compared with LIBS and LIBS-RE-OFF, plasmas in LIBS-RE-ON showed larger spatial expansion and enhanced emission after a delay time of 1 µs in this study, as well as significantly enhanced electron temperature by ∼ 64%. Time-resolved electron temperatures and densities showed that the emission signal enhancement in LIBS-RE-ON can be primarily attributed to the electron temperature enhancement. Signal enhancement in LIBS indicated improved detection sensitivity. This study could inspire future works on LIBS for gas detection with improved sensitivity and selectivity probably by using ultrafast/intense laser-induced molecular breakdown/ionization with resonant vibrational excitation of molecules.

Original languageEnglish (US)
Pages (from-to)1197-1205
Number of pages9
JournalOptics Express
Volume28
Issue number2
DOIs
StatePublished - Jan 20 2020

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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    Yang, G., Liu, L., Wang, T., Fan, L., Huang, X., Tian, D., Jiang, L., Silvain, J. F., & Lu, Y. (2020). Laser-induced breakdown spectroscopy of ammonia gas with resonant vibrational excitation. Optics Express, 28(2), 1197-1205. https://doi.org/10.1364/OE.382663