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  1. Pressure scaling of collisional broadening parameters of krypton (absorber)4p6S01→<#comment/>→<#comment/>5p[3/2]2transition centered at 107.3 nm in the presence of nitrogenN2(perturber) is investigated. The absorption spectrum in the vicinity of the transition is obtained from the two-photon excitation scan of krypton in the presence of the perturber at different prescribed pressures varying from a few torrs to 10 atm. The absorption spectra reveal noticeable asymmetry at atmospheric pressure, and the asymmetry becomes increasingly pronounced with pressure; however, the absorption spectra at sub-atmospheric pressures tested are symmetric. The absorption spectra are fitted with synthetic asymmetric Voigt profiles across all pressures, wherein the asymmetry parameter is varied to capture the asymmetry at different pressures. The collisional shift (δ<#comment/>C), the symmetric equivalent collisional full width at half maximum (wC,0), and the asymmetry parameter (a) are determined from the synthetic fits at various pressures. All the parameters are observed to vary linearly with pressure over the entire range of the pressure values tested. The mechanisms that cause the asymmetry in the absorption spectra are also discussed.

  2. Temperature scaling of collisional broadening parameters for krypton (absorber)4p6S01→<#comment/>5p[3/2]2electronic transition centered at 107.3 nm in the presence of major combustion species (perturber) is investigated. The absorption spectrum in the vicinity of the transition is obtained from the fluorescence due to the two-photon excitation scan of krypton. Krypton was added in small amounts to major combustion species such asCH4,CO2,N2, and air, which then heated to elevated temperatures when flowed through a set of heated coils. In a separate experimental campaign, laminar premixed flat flame product mixtures of methane combustion were employed to extend the investigations to higher temperature ranges relevant to combustion. Collisional full width half maximum (FWHM) (wC) and shift (δ<#comment/>C) were computed from the absorption spectrum by synthetically fitting Voigt profiles to the excitation scans, and their corresponding temperature scaling was determined by fitting power-law temperature dependencies to thewCandδ<#comment/>Cdata for each perturber species. The temperature exponents ofwCandδ<#comment/>Cfor all considered combustion species (perturbers) were−<#comment/>0.73and−<#comment/>0.6, respectively. Whereas the temperature exponents ofwCare closer tomore »the value (−<#comment/>0.7) predicted by the dispersive interaction collision theory, the corresponding exponents ofδ<#comment/>Care in between the dispersive interaction theory and the kinetic theory of hard-sphere collisions. Comparison with existing literature on broadening parameters of NO, OH, and CO laser-induced fluorescence spectra reveal interesting contributions from non-dispersive interactions on the temperature exponent.

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