Flame spectrum

For visual observation of the cell interior through the sapphire windows a lamp mounted behind one end is used. A mirror and stereo microscope at the other end facilitate the observation. The microscope is equipped with a normal camera or a video camera. Normally the phenomena within the cell are continuously observed and controlled with video camera and colour monitor. A video recorder serves for documentation, for inspection of short time processes and for the production of standing flame pictures for size and shape determination. Instead of the microscope a Jarrell-Ash diode array rapid scan spectrometer can be attached to the cell to obtain flame spectra in the visible and UV-regions. 

Combustion (Flame) Temperature of Propellants Measurements. Optical methods are the most widely used for the measurement of flame temperature. Since the study of a flame depends not only on temperature, but also on other factors (the radiation factor, the chemical reactions in the gases, etc), it is necessary first of all to study the spectral characteristics of the objects under investigation. Flame spectra were studied in Russia on the ISP-51 spectrograph... 

In recent wrork particular emphasis has been given to studies of flame spectra and the evidence as to the formation and reaction of excited species such as C2, CH, OH, and HCO from acetylene and oxygen (17, 29, 31, 41, 43, 54). The occurrence of excited hydrocarbon flame bands attributable to HCO radicals led Herman, Hombeck, and Laidler (31) to suggest the reaction... 

At present it seems that no proposed mechanism can successfully explain all observations on flames, flame spectra, and the tracer experiments. 

The nature of the radiation processes is not fully understood. Ball (10,11), with the aid of a stroboscopic shutter, visually observed cool flames as actual flame fronts moving across the combustion chamber of a motored engine. This was later confirmed by Getz (53). The source of cool flame emission in tube experiments has been attributed to excited formaldehyde by Emeleus (51) and Gaydon (52). Cool flame spectra in engines obtained by Levedahl and Broida (70) and Downs, Street, and Wheeler (35) were reported to be due to excited formaldehyde. The nature of the blue flame spectra has not been fully explored, although some evidence points to carbon monoxide emission (35). 

Characteristics of the main lines and bands of rare earth elements in oxygen-hydrogen flame spectra [184]. 

Spectroscopic tests. Flame spectra The only worthwhile way to employ flame tests in analysis is to resolve the light into its component tints and to identify the cations present by their characteristic sets of tints. The instrument employed to resolve light into its component colours is called a spectroscope. A simple form is shown in Fig. II.3. It consists of a collimator A which throws a beam of parallel rays on the prism B, mounted on a turntable the telescope C through which the spectrum is observed and a tube D, which contains a scale of reference lines which may be superposed upon the spectrum. The spectroscope... 

Flame spectra with nitrogen oxide as combustion partner) 2) H. 

Behrens F. Rossler, ZNaturforsch 6a, 154-60(1951) CA 45, 8361 (1951)(Flame spectra of systems with NOa— bound oxygen)... 

F3. Fassel, V. A., Myers, R. B., and Kniseley, R. N., Flame spectra of vanadium, niobium, rhenium, titanium, molybdenum, and tungsten. Spectrochim. Acta 19, 1187-1194 (1963). 

There are two kinds of flame spectra high temperature gas produces atomic and molecular spectra and high temperature solid or liquid particles produce continuous spectra. Important spectra are as follows (1) Strontium spectra(Fig. 2) b... 

Ca-Cl) = 102+6 kcal mol" from flame spectra studies. This leads to AjH (CaCl, g. 

The adopted A H (Ca0H, g, 0 K) -flame spectra of CaOH, SrOH, and BaOH. 

From observations made during a flame spectra study of the bond dissociation energy of magnesium oxide, Cotton and Jenkins... 

The value of D (Mg-OH) = 56 5 kcal mol derived by Bulewicz and Sugden (8) from flame spectra studies appears to be too... 

The same system was used to record temporal data from a H2/air flame using spectral band-pass filters. Fig. 6 shows water flame spectra obtained under two different flame conditions a near stoichiometric flame and a lean flame. The spectral data match the known theoretical spectra of water. The width of the spectral band is an indicator of water temperature. Thus, we can determine the density and temperature of the water vapor within the flame using a set of three spectral bands corresponding to the center and wing of the water band, and a null band outside of the water radiation band. 

Schematic representation of instrumentation for flame spectra photometric procedures ...

Talbot (Tl) had previously studied the flame spectra of lithium and strontium, but the full potentialities of Herschel s observations for qualitative analysis were first realized in the work of Kirchhoff and Bunsen (Kl). These authors discovered cesium in 1860 and rubidium in the following year by observation of their flame spectra. 

In the 1820s, David Brewster (1781-1868), Sir John Herschel (1792-1871), and William Henry Fox Talbot performed similar types of experiments on the absorption of light to those by Fraunhofer. Independently, these researchers made the observation that flame spectra obtained by burning compounds of different compositions varied in systematic ways. These three researchers all produced line spectra, which they tried to relate to the dark lines observed by Fraunhofer... 

The existence of the hydroxyl radical as a separate. If transient, entity was first recognized in 1924 by Watson (19), who proposed that the water vapor bands emitted by flames and electric discharges In moist air were due to the OH radical, and not to excited H2O. In 1928 Bonhoeffer and Relchardt (20) obtained the absorption spectrum of the OH radical in partially dissociated water vapor at v>1873°K, and In 1935 Oldenberg (21) was able to follow the decay of the radical In the products flowing from an electric discharge through water vapor. This latter work was of Importance since the OH radical could then be monitored In a system applicable to kinetic studies. Early combustion studies showed that the hydroxyl radical Is also an Important constituent of flames, the most prominent feature of flame spectra (22) being emission from the (a2i + - X Il) band system of the OH radical. 

Flaud, J.-M., Camy-Peyret, C., Maillard, J.P Higher ro-vibrational levels of H2O deduced from high resolution oxygen-hydrogen flame spectra between 2800-6200 cm . Mol. Phys. 1976, 32, 499-521. 

In 1802 Wollaston discovered, in the continuum emission spectrum of the sun, dark lines which were later studied in detail by Frauenhofer. He observed about 600 lines in the sun s spectrum and named the most intensive of them by the letters from A to H. In 1820 Brewster explained that these lines originate from the absorption processes in the sun s atmosphere. Similar observations were made by several researchers in the spectra of stars, flames, and sparks. In 1834 Wheatstone observed that the spectra produced with a spark depended on the electrode material used. Angstrom in turn made the observation that spark spectra were also dependent on the gas surrounding the electrodes. The study of flame spectra became much easier after the discovery of the Bunsen burner in 1856. 

Kirchhoff and Bunsen constructed a flame spectroscope in 1859. This new instrument made it possible to study small concentrations of elements which was impossible by the other methods available at that time. They also showed that the lines in the flame spectra originated from the elements and not from the compounds. Applications for this new technique were soon observed in astronomy and analytical chemistry. In the next five years, four new elements (Rb, Cs, Tl, and In) were found by flame emission spectroscopy. 

The value of C, as has been explained, depends upon the nuclear charge less the screening effect of other electrons. For the K series of X-ray frequencies it varies nearly as Z. As the degree of ionization of the atom increases with more intense methods of spectral excitation, for example, passage from flame spectra to spark spectra, G increases. For the spectrum of ionized helium (nuclear charge 2, one electron) it is four times the value for hydrogen (nuclear charge... 

There is a voluminous hterature concerned with the study of flame spectra, but the application of spectroscopy to the study of flame kinetics followed the introduction of flame photometry as a general analytical tool. The chief interest before this was in the spectra of the flames, which could serve to demonstrate the presence of intermediates in the combustion process. These were in general detected by the emission spectra of excited species and therefore were not necessarily indicative of the concentrations of ground state species. The difficulties of constructing burners which were sufficiently large and uniform to allow the study of absorption spectra prohibited a measurement of the species in their ground states, until the development of the multiple pass technique. ... 

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