Article
Version 1
Preserved in Portico This version is not peer-reviewed
Hydroxyl Spectroscopy of Laboratory Air Laser-Ignition
Version 1
: Received: 12 September 2022 / Approved: 13 September 2022 / Online: 13 September 2022 (09:59:03 CEST)
A peer-reviewed article of this Preprint also exists.
Parigger, C.G. Hydroxyl Spectroscopy of Laboratory Air Laser-Ignition. Foundations 2022, 2, 934-948. Parigger, C.G. Hydroxyl Spectroscopy of Laboratory Air Laser-Ignition. Foundations 2022, 2, 934-948.
Abstract
This work investigates spatial and temporal distributions of hydroxyl, OH, in laser-plasma in laboratory air at standard ambient temperature and pressure. Of interest are determination of temperature and density of OH and establishment of a correlation of molecular OH emission spectra with shadow graphs for time delays of 50 to 100 microsecond, analogous to previous work on shadow graph and emission spectroscopy correlation for cynaide, CN, in gas mixtures and for time delays of the order of 1 microsecond. Wavelength- and sensitivity- corrected spatiotemporal data analysis focuses on temperature inferences using molecular OH emission spectroscopy. Near-ir radiation from a Q-switched laser device initiates optical breakdown in laboratory air. The laser device provides 6 nanosecond, up to 850 milli Joule pulses at a wavelength of 1064 nanometer, and focal irradiance in the range of 1 to 10 Tera Watt per centimeter-squared. Frequency doubled beams are utilized for capturing shadow graphs for visualization of the breakdown kernel at time delays in the range of 0.1 to 100 microsecond. OH emission spectra of the laser plasma, spatially resolved along the slit dimension, are recorded in the wavelength range of 298 nm to 321 nm, and with gate widths adjusted to 10 microsecond for the intensified charge-coupled device that is mounted at the exit plane of a 0.64 m Czerny-Turner configuration spectrometer. Diatomic OH signals occur due to recombination of the plasma and are clearly distinguishable for time delays larger than 50 microsecond, but are masked by spectra of N2 early in the plasma decay.
Keywords
molecular spectroscopy; diatomic molecules; optical emission spectroscopy; laser induced optical breakdown; hydroxyl; nitrogen second positive; cynaide; atomic spectroscopy; plasma physics; astrophysics
Subject
Physical Sciences, Atomic and Molecular Physics
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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