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M. Lino da Silva

Publications and source records attributed to M. Lino da Silva.

4 recordsLinked to original sources
arXiv2022

Unfocused laser ignition of high-pressure He-H2-O2 combustible mixtures

We report consistent ignition of high-pressure (p > 20-30 bar) hydrogen-oxygen mixtures diluted with helium, using an unfocused Nd:YAG laser. This corresponds to laser irradiances several orders of magnitude below the minimum ignition energies reported in the literature. By placing a mirror inside a cylindrical vessel and filling it up to 100 bar with H2-He or O2-He non-combustible mixtures, we obtain the pressure-dependent absorptivity of the combustible He-H2-O2 mixture. We find no measurable absorption of the laser signal by the medium, for the overall pressure range, to the experimental apparatus sensitivity (about 1% of the laser irradiance). This leads credence to the theory that ignition stems from seed electrons created by autofocusing ionization of dust/impurities in the gas.

physics.chem-ph↗
arXiv2020

Comment on "Collision and radiative processes in emission of atmospheric carbon dioxide"

Recently, Smirnov published a paper (B. M. Smirnov, "Collision and radiative processes in emission of atmospheric carbon dioxide", 2018, J. Phys. D.: Appl. Phys., Vol. 51, No. 21, pp. 214004) which dismisses the role of increasing concentrations of anthropogenic CO$_2$ on global warming of planet Earth. We show that these conclusions are the consequence of two flaws in Smirnov's theoretical model which neglect the effects of the increased concentrations of CO$_2$ on the absorption of Earth's blackbody radiation in the 12-15$μ$m region. The influence of doubling the concentration of CO$_2$ in the atmosphere on the surface temperature is not $Δ$T=0.02K, or even $Δ$T=0.4K if only one of the two mistakes in Smirnov's analysis is corrected. The correct value lies within $Δ$T=1.1-1.3K as outlined by other authors analysis using simplified, yet more theoretically consistent models.

astro-ph.EP↗
arXiv2005

Guidelines for the Calculation of Bound Molecular Spectra

Line-by-line calculations are becoming the standard procedure for carrying spectral simulations. However, it is important to insure the accuracy of such spectral simulations through the choice of adapted models for the simulation of key parameters such as line position, intensity, and shape. Moreover, it is necessary to rely on accurate spectral data to guaranty the accuracy of the simulated spectra. A discussion on the most accurate models available for such calculations is presented for diatomic and linear polyatomic discrete radiation, and possible reductions on the number of calculated lines are discussed in order to reduce memory and computational overheads. Examples of different approaches for the simulation of experimentally determined low-pressure molecular spectra are presented. The accuracy of different simulation approaches is discussed and it is verified that a careful choice of applied computational models and spectroscopic datasets yields precise approximations of the measured spectra.

physics.optics↗