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

Single Laser Detection of CO and OH via Laser Induced Fluorescence

Two-photon laser-induced fluorescence detection of carbon monoxide with excitation in the Fourth Positive System near 280 nm is demonstrated in carbon monoxide/nitrogen mixtures at ambient conditions and in a methane/air Bunsen flame. Fully resolved rotational spectra are presented for the A–X (5,0) and (4,0) bands near 279 and 284 nm, respectively. Energy transfer from excited molecular nitrogen to carbon monoxide with subsequent fluorescence from carbon monoxide that was reported for low pressure conditions in the literature has also been observed at atmospheric conditions. It was further demonstrated that overlaps of some CO A–X (4,0) rotational lines with OH A–X (1,0) rotational lines allow simultaneous excitation of both species with a single laser. The fluorescence bands are completely separated, enabling detection without crosstalk. Detection limits are adequate to detect CO in nascent state in a flame and it is expected that for application in high-pressure, low-temperature combustion environments, where high quantities of CO are present, this approach can provide advantages compared to the excitation of CO at shorter wavelengths due to decreased laser beam attenuation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86784/1/Sick6.pd