Measurement and analysis of OH emission spectra following laser-induced optical breakdown in air

Abstract

The measured emission spectra of the OH radical subsequent to laser-induced optical breakdown in air are analyzed to infer spectroscopic temperature and species number density. Emissions from the UV A2sigma+ --> X2IIi transition dominate the spectra in the wavelength range of 306-322 nm and for time delays from the optical breakdown of 30-300 micros. Contributions from other species to the recorded OH emission spectra were also investigated for spectroscopic temperature measurements in the range of 2000-6000 K and for OH number densities in the range of 10(14) - 2 x 10(16) cm(-3). Monte Carlo simulations are applied to estimate errors in the analysis of the hydroxyl spectra.

Atomic and molecular emissions in laser-induced breakdown spectroscopy

“…1). Molecular recombination emission spectra [82] can be measured for time delays on the order of 1 to a few 10s of microseconds after LIB.…”

“…Analysis of the recorded hydrogen spectra include measurements of full-width-half-maximum (FWHM) and full-width-half-area (FWHA) to infer electron number density N e [76]. Temperature was determined from incomplete hydrogen Balmer Series lines [103]. Yet for time delays on the order of 1 μs, molecular emissions can be recognized from the C 2 Swan system, superposed to the H β and H γ Balmer series lines.…”

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

“…This sort of spectrum is frequently observed in many kinds of flames and hot gases containing oxygen and hydrogen [24,25]. The OH spectrum is also observed in the range of wavelength of 306-320 nm [26] and 306-322 nm [23]. These features are clearly seen in Fig.…”

“…They proposed neutron diffraction to confirm the formation of hydroxo like group. However, the hydroxo group (OH band) has been observed in several other studies in the wavelength range of 306-322 nm [23]. So, the optical emission spectra were obtained and analyzed during the reduction study.…”

Analysis of time-resolved superposed atomic hydrogen Balmer lines and molecular diatomic carbon spectra

“…The inferred temperature for the diatomic molecular spectra amounts to approximately 5000 K. The error in determining the molecular temperature is estimated to be on the order of 500 K. This error is due to several factors, for example, including accuracy of wavelength calibration, determination of baseline offset, experimental noise associated with use of the optical multichannel analyzer, and signal-tonoise ratio for the molecular C 2 spectra. Previous studies of LIB in air [25] utilized extensive Monte Carlo simulations to evaluate the temperature uncertainty from OH measurements. A similar approach for the C 2 spectra is expected to yield molecular temperature and an error distribution within 500 K. The corresponding electron temperature, T e , is determined from Balmer series Boltzmann plots.…”