Flame Emission Spectra Research Articles

New analysis of the C 2 Ballik-Ramsay system from flame emission spectra

The C 2 b 3Σ g − → a 3Π u Ballik-Ramsay system has been studied through emission flame spectra recorded with a Fourier transform interferometer. The 14 bands 0-0, 1-0, 1-1, 2-0, 2-1, 3-0, 3-1, 3-2, 4-1, 4-2, 5-2, 5-3, 6-3, and 7-4 were identified in the 4850- 9900-cm −1 spectral range. They have been reduced to molecular constants using an iterative, nonlinear, least-squares method. Rotational perturbations, observed in the b 3Σ g − v = 0, 1, 2, 5, and 6 levels, have been reduced. Dunham coefficients are obtained for both the b 3Σ g − and a 3Π u states.

Selective excitation of molecular species in flames by laser-excited molecular fluorescence

Abstract Pulsed tunable dye laser excited (nitrogen laser pumped) molecular fluorescence spectra of BaO, BaOH, and BaCl in an air-acetylene flame have been investigated and compared to the flame emission spectra of the same species. Molecular fluorescence of BaO and BaOH in flames was observed for the first time. Furthermore, BaO, BaOH and BaCl which have overlapping emission spectra in the wavelength region from 480 to 535nm can be selectively excited and observed by laser excited molecular fluorescence spectroscopy.

The “in-flame-reaction” method for Al 2O 3 aerosol formation

In this paper a study was made of the conditions of formation and properties of Al 2O 3 aerosol obtained by oxidation of aluminium acetylacetonate ultrasonically sprayed into a hydrocarbon-oxygen flame. Spherical particles with diameters as small as 30 Å were obtained at sprayer frequency ν = 1 MHz as a result of rapid combustion. Temperature measurements and investigation of the flame emission spectrum as well as of the shape and size of particles suggest that liquid Al 2O 3 droplets are formed from the gaseous phase next to be crystallized from the liquid phase. Comparison of the results concerning Al 2O 3 formation in H 2 + O 2 flame and in the hydrocarbon-oxygen flame leads to the suggestion that the γ-Al 2O 3 phase is formed if synthesis and crystallization occurs in the presence of the H 2O and/or OH and the liquid particles are rapidly cooled. The following scheme of the aerosol formation mechanism is proposed: ▪ [Al 2O 3] L. OH ads denotes Al 2O 3 particle with chemisorbed OH.

Flame emission studies of ozone with metal alkyls: Zn (CH 3) 2 and Zn (C 2H 5) 2

Resolved flame emission spectra from the reaction of ozone, O 3, with zinc dimethyl, Zn(CH 3) 2, and zinc diethyl, Zn(C 2H 5) 2, in a flow system at about one torr pressure reveal a number of interesting electronically-excited species. The Zn(CH 3) 2 + O 3 flame has a pale blue appearance, characteristic of the “cool flame” bands of CH 2O, while the Zn(C 2H 5) 2 + O 3 flame has a deep blue appearance caused by ZnH ∗ emission. In addition the reaction of O 3 with H atoms resulting probably from the decomposition of C 2H 5 radicals in the latter reaction leads to strong OH † ( 2π i) emission (Meinel bands). Also, OH ∗ ( 2Σ +) emission is observed and is found to have a quadratic dependence on OH †. Mechanisms involving the different chemistry of CH 3 and C 2H 5 radicals in the flame are proposed to account for these observations.

The Influence of Water Vapour on the Emission Spectra of Flames

Abstract The infrared emission spectra of a variety of small diffusion flames was studied in the laboratory. Ethylene, acetylene, matchwood and the pyrolysis products of Eucalypt forest litter gave qualitatively similar spectra consisting largely of non-specific black body radiation from carbon particles, with narrow radiation bands due to water vapour and, especially, carbon dioxide. Addition of water to the fuels had little effect on the carbon dioxide emission but reduced the radiation from the carbon particles by a factor as large as three. The effect arises from changes in the opacity of the flames. This result goes far toward explaining the profound influence which fuel moisture has on the rate of spread of a forest fire

The spectral distribution of radiant energy of a gas-fired radiant panel and some diffusion flames

Measurements were made of the spectral distribution of energy from radiant sources employed in standard test methods of flammability. Radiant sources examined were a gas-fired radiant panel employed in ASTM Test E-162 and the electric heater employed in the Smoke Chamber Test. To afford a basis for comparison, the emission spectra of several diffusion flames in air were measured. The energy distribution of the flames occurred essentially in two narrow wavelength intervals corresponding to emission of carbon dioxide at 4.4 μm and water at 2.7 μm. Luminous diffusion flames containing large amounts of incandescent carbon, such as occur from the combustion of acetylene-in-air, show a blackbody background continuum with CO 2 and H 2 O emission peaks superimposed on the continuum. The radiant test sources exhibited an energy distribution approximating that of a blackbody with atmospheric CO 2 and H 2 O absorptions superimposed. The gas-fired radiant panel in addition showed a significant emission peak at 4.4 μm due to excited CO 2 .

Spectra and temperature of propellant flames during depressurization

Composite propellant flame temperature and emission spectra during depressurization by rarefaction waves, using rapid scanning spectrometer

Hydrocarbon Flames as Reference uv Light Sources

Premixed hydrocarbon–air flames stabilized on Meker burners are proposed for use as reference sources of ultraviolet (uv) light. A measure for the uv light intensity output is given by the flame chemi-ionization. The ratio of optical energy output per unit of electrical charge generated is a function of the wavelength band of the flame emission spectrum but is independent of size of the flame, applied electric field required for measuring flame ionization, burner–electrode configuration, temperature, and of small fluctuations of pressure and composition of the hydrocarbon fuel. An approximate, average value of 8 · 10−3 J/C was determined for the 2000–2100-Å spectral band of a stoichiometric, premixed methane–air flame.

On Intensity Alterations in C2 “Swan” Emission Spectra

The presence of intensity alternations in C2 Swan emission spectra of flames is analyzed. It is argued that the nonequilibrium rotational energy distribution is caused by collision-induced electronic transitions between the radiating A 3Πg state and the vibrationally excited A′3Σg− or A″3Σu+ states of C2. The selection rules are derived on the basis of the parity properties of the relevant states and the various terms of the multipole expanded interaction potential. The selection rules lead to an unambiguous choice between the collision-induced transitions A″3Σu+→A 3Πg or A 3Πg→A′3Σg−. On the basis of available experimental information of the pressure dependence of the effect, additional evidence is given that a formation process is responsible for the occurrence of the intensity alternations. Examples of intensity alternations in Si2 and N2 are briefly discussed.

Further observations of chemiluminescence in diffusion flames of alkali metals and halogenated methanes

Emission spectra of low-pressure diffusion flames of haloforms or carbon tetrahalides burning in potassium or sodium vapor have been studied at moderate resolution. Spectra of the tetrahalide flames are very rich in C 2 emission. The spectrum of the CCl 4 −K flame is found to contain about 150 new bands of C 2 that can be measured and assigned with the aid of calculations of band heads or origins. The new bands are found to include transitions of the Swan, Ballik-Ramsay, and Phillips systems, plus transitions from four previously unobserved, forbidden systems. All of the new systems involve known states of C 2 . Some discussion and observations are included on the origins of the chemiluminescence, on populations, and on the effects of additives.

A photometric study of the emission spectra of cyanogen flames at reduced pressure

This paper follows from an earlier publication, in which observations on highly nonthermal ionization in low-pressure C2N2−O2 flames were reported. Here, emission features of these and similar flames were studied and photometric measurements were made, under a variety of conditions, on the red and violet CN systems, C2 Swan bands, NCN bands and NO+O incandescence. The temperatures and equilibrium compositions of the flames were calculated with the aid of a computer program. The results showed that the major part of the visible and ultraviolet emission from the flames examined was nonthermal in origin. In the case of the CN bands, the intensity distribution among the various vibrational transitions within the violet system was also found to be anomalous, transitions with ν′≥5 being considerably enhanced. All band intensities depend upon the square of the total pressure, and chemiluminescence can probably be attributed to very energetic three-body reactions. There is no obvious link between chemiluminescence and chemiionization, which is also observed in these flames, except that both phenomena are probably associated with excess atom and free radical concentrations.

Flame Photometer Specialized for Cesium

A new photometer system is described that allows very small traces of an element, such as cesium, to be determined quantitatively with greater precision than previously possible with flame-emission spectra. For example, with the new system it is possible to replicate measurements of the cesium in quantities that are normally present in one liter of sea water (about 0.3 μg) with standard error less than two percent. Dilute cesium standard solutions can be compared significantly within a few parts per billion. This, apparently, has not been reported for any previous flame photometer. The system consists of two photomultiplier tubes observing a flame simultaneously, from the same aspect, but each having a different optical filter interposed. Use is made of a beam splitter and two interference filters, one filter passing only a narrow band centered at the 8521.1-Å line of cesium, the other filter passing a nearby band not containing much of this emission but rather passing a sample of the background of the flame that contributes much of the total statistical fluctuation. Signals from these two phototubes are compared by suitable differential circuits, and are continuously recorded. A specialized automatic sample-changing system was developed to provide for precise timing of the burning of the sample and the standard solutions and to carry out aspirator washings immediately following the burning of each sample. Finally, means are provided for continuously monitoring the aspiration rate by recording the brightness of the background (off-peak) signal independently.

Spectroscopic studies of the effect of inhibitors on counterflow diffusion flames

A quantitative study of the emission spectra of counterflow diffusion flames of ethylene, methane or hydrogen burning with air has been made when inhibitors (methyl bromide, bromine, carbon tetrachloride, chlorine or phosphorus oxychloride) are added to either the air or fuel supply. Specific effects occur for various fuels and inhibitors, but in general, OH and HCO emission decreases, C 2 increases, and CH varies little as the inhibitor concentration increases. Carbon luminosity usually increases, and this is accompanied by a fall in flame temperature. Results are discussed on the assumption that the inhibitor removes OH radicals, thereby slowing the oxidation processes, and also promotes polymerization and carbon formation which increases radiation losses and cools the flame.

Analytical applications of the flame emission spectra of lead and titanium

The flame emission spectra of lead and titanium, weak emitters in an oxy-hydrogen flame, have been studied with a view to their analytical applications. Interference effects, especially on the titanium emission band at λ 518 mμ, and methods for eliminating or reducing them, have been investigated. Methods for determining lead and titanium in their respective alloys, by the use of a standard addition technique, have been developed. These methods have been tested on suitable alloys; the results have a reproducibility of ± 4–5% (coefficient of variation). The advantages and the limitations observed in this study have a general bearing on the application of flame photometry to other elements.

Flame photometric determination of yttrium

A flame photometric method for the determination of yttrium in yttrium group rare earths is presented. There were three characteristic peaks in flame emission spectrum of yttrium, and two of them (599 m mu , 615 m mu ) were used to determine the amount of yttrium in 0.1N hydrochloric acid solution. The relation between log. amount of yttrium and log. intensities of the flame spectra is shown. The amount of yttrium in the impure yttrium solution extracted from xenotime was determined. The effectiveness of the method was recognized by the satisfactory recovery of yttrium added to the impure yttrium solution. It is recommended for industrial analysis. (auth)

Emission spectra of flames supported by active nitrogen

The first page of this article is displayed as the abstract.

Infrared emission spectra of ammonia-oxygen and hydrazine flames

Abstract The infrared emission spectra of a hydrazine decomposition flame and of an ammonia-oxygen diffusion flame have been studied with high-resolution grating spectrometers in the spectral range 600–4000 cm−1. Emission spectra of the hydrazine flame were recorded at various heights in the flame and at two burning pressures. High-resolution absorption spectra of ammonia and hydrazine vapor have been recorded on the same scale for comparison. Emission spectra have also been recorded from two areas of the ammonia-oxygen diffusion flame, one in the ammonia-rich part of the flame and the other in the region of intense yellow radiation due to the NH2 radical. An oxy-hydrogen diffusion flame was examined to establish the spectrum emitted by hot water vapor and by the OH radical. The high-resolution absorption spectrum of ammonia was again recorded on the same scale. There are many emission lines from the hydrazine decomposition flame which can be assigned neither to ammonia nor to hydrazine. These lines are pointed out and discussed, but no definite assignment seems possible from the data because of the large number of short-lived species that might exist in this flame, all containing only nitrogen and hydrogen, and hence all having their infrared bands in similar spectral regions. Nearly all of the emission lines from the ammonia-oxygen flame have been assigned to water, ammonia or the OH radical. Several lines of uncertain assignment appear near 1100 cm−1. These may be due to ammonia, but no correlation exists between them and the ammonia absorption spectrum such as is found in other regions. The most striking new lines are found in the region 2700–3050 cm−1, where a series of twenty-three almost evenly spaced lines occur which cannot be assigned to known lines of water, ammonia or OH. The new lines have tentatively been ascribed to the NH2 radical. In the emission of both flames, the R-branch of the band due to the inversion vibration at 950 cm−1 in ammonia is easily visible, but the P-braneh is not. This phenomenon is attributed to an effect, previously observed in diatomic molecules, which increases the intensity of either the P-branch or the R-branch of a band at the expense of the other branch.

Infrared emission spectra of flames under high resolution

Infrared emission spectra of flames under high resolution

Emission and absorption spectra of flat flames

The multiple reflection absorption technique has been applied to flat flames. The presence of oxidation and pyrolysis intermediates in rich-limit flat flames has been shown by their ultraviolet absorption spectrum. Formaldehyde and benzene have been detected in flames of ether and hexane with air. There is also weak absorption in the region 2,750in the case of the hexane flame. This could be attributed to absorption by a cyclic radical or molecule. Early results of the application of the multiple reflection technique to low-pressure flames have given the absorption bands due to OH and NH. The emission spectra of the Egerton-Powlingflames of various fuels near the rich and weak limits of combustion are recorded. It is found that the emission spectrum of the rich diethyl-ether flame varies in a similar way to that indicated by Agnew and agnew but some details of a qualitative nature are added. The occurrence of the hydrocarbon flame bands and the possible relationship with the conditions of occurrence of the cool flame bands are briefly discussed. Observations of the emission and absorptionspectra of flames burnt on a porous plate burner are mentioned.

Infrared flame spectra

This paper presents a summary of recent work on the emission spectra of hydrocarbon flames in the region from 1 to 5.5 microns. The temperature of flames as determined by intensities of the infrared rotational and vibrational bands is found to be about 2600° K. Further temperature measurements on the incandescent particles in an oxyacetylene flame have been made and it was found that the values determined agree with those obtained from the spectral measurements.