Infrared emitting species

Smit, K.J., Hancox, R.J., Hatt, D.J., Murphy, S.P. and de Yong, LV. (1997) Infrared emitting species identified in the combustion of boron-based pyrotechnic compositions. Appl. Spectrosc., 51, 1400-1404. 

The emitting species for sulfur compounds is excited S2. The lambda maximum for emission of excited S2 is approximately 394 nm. The emitter for phosphorus compounds in the flame is excited HPO with a lambda maximum equal to doublet 510-526 nm. In order to detect one or the other family of compounds selectively as it elutes from the GC column, the suitable band-pass filter should be placed between the flame and the photomultiplier tube to isolate the appropriate emission band. In addition, a thermal infrared filter is mounted between the flame and the photomultiplier tube to isolate only the visible and UV radiation emitted by the flame. Without this filter, the large amounts of infrared radiation emitted by the combustion reaction of the flame would heat up the photomultiplier tube, thus increasing its background signal. 

A picture of the infrared emission profile for the dissociation of hydrogen chloride, highly dilute in argon, is shown in Fig. 2. The proportionality of emission signal to concentration has to be demonstrated before kinetic analysis of the profile. The sweep speed of the oscilloscope for this particular experiment was set at 10 psec cm . The first 26 /isec of the recorded time depicts the unshocked gas at its initial pressure at room temperature. The sudden increase in the emission signal is caused by shock arrival at the observation window and is followed by the disappearance of the emitting species as it decomposes. The total reaction time is of the order of 70 jusec. 

It is scenario 3 that is most consistent with the data depicted in Fig. 1-2. Given that the physical climate system is strongly influenced by gases in the atmosphere that absorb and emit infrared radiation (e.g., H2O, CO2, CH4, etc.), and since the amounts of these species in the air depend to some extent (for some, a great extent) on the functioning of the biosphere, it is logical to view the climate of the Earth as a coupled physical, chemical, and biological entity. 

The nitric oxide reacts with ozone to produce an electronically excited specie (N02 ) that decays back to its ground state emitting light in the infrared spectral region (600-2800 nm). 

So far, we have been concerned mainly with emission of radiation from electronically excited states. Emission may also arise from vibrational transitions in various reaction systems. The species HO2 has long been postulated as an important chain carrier in combustion reactions, although emission from electronically excited HO2 has yet to be demonstrated unequivocally. However, Tagirov has observed radiation in flames at a frequency of 1305 cm which he ascribes to transitions from vibrationally excited HO2. Investigations of vibrational quenching processes are of great interest, and if the vibrationally excited species emit infrared radiation, then emission spectrometry may be the most satisfactory way of following the reaction. Davidson et describe a shock-tube study of the relaxation of... 

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