Current assessment of the Red Rectangle band problem

In this paper we discuss our insights into several key problems in the identification of the Red Rectangle Bands (RRBs). We have combined three independent sets of observations in order to try to define the constraints guiding the bands. We provide a summary of the general behavior of the bands and review the evidence for a molecular origin of the bands. The extent, composition, and possible absorption effects of the bands are discussed. Comparison spectra of the strongest band obtained at three different spectral resolutions suggests that an intrinsic line width of individual rotational lines can be deduced. Spectroscopic models of several relatively simple molecules were examined in order to investigate where the current data are weak. Suggestions are made for future studies to enhance our understanding of these enigmatic bands

Attenuation corrections for in-cylinder NO LIF measurements in a heavy-duty Diesel engine

Contains fulltext : 36058.pdf (publisher's version ) (Closed access)Quantification of the nitric oxide (NO) concentration inside the cylinder of a Diesel engine by means of laser-induced fluorescence (LIF) measurements requires, amongst others, knowledge of the attenuation of the ultraviolet radiation involved. We present a number of laser diagnostic techniques to assess this attenuation, enabling a correction for laser intensity and detection efficiency of the raw NO LIF data. Methods discussed include overall laser beam transmission, bidirectional laser scattering (bidirectional LIF), spectrally resolved fluorescence imaging, and Raman scattering by N-2. A combination of techniques is necessary to obtain the complete attenuation of laser beam and NO fluorescence. The overall laser beam transmission measurements and bidirectional LIF measurements (the latter yielding spatially resolved transmission) provide evidence of a non-uniform attenuation distribution, with predominant attenuation within or near the piston bowl. Fluorescence imaging of multiple vibrational bands through a spectrograph is shown to be a powerful method for obtaining spatially resolved data on the transmission losses of fluorescence. Special attention is paid to the role of CO2 and O-2 as UV light absorbers, and the consequences to different excitation-detection schemes for NO

Absorption cross-sections of atmospheric constituents: NO2, O2, and H2O

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO2, O2 and its collision-induced absorption spectrum, and H2O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth's atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.info:eu-repo/semantics/publishe