Halogen atomic emission

O2 and Bra, the strong halogen atom emission probably arises from predissociation of the excited ArX state, and the total atomic and ArX emissions account for the bulk of the quenching in these cases also. ... 

The presence of heteroatoms usually provides a convenient feature for improving selectivity by employing selective detection mechanisms. GC may then use flame photometric detection (FPD) for S and P atoms and to a certain extent for N, Se, Si etc. thermoselective detection (TSD) and nitrogen-phosphorus detection (NPD) for N and P atoms electron capture detection (ECD) for halogen atoms (E, Cl, Br, and 1) and for systems with conjugated double bonds and electron-drawing groups or atomic emission detection (AED) for many heteroatoms. 

Table I. Photoelectric Mass Absorption Coefficients of Halogen Atoms and of Carbon, Oxygen, Hydrogen at 8.34 A (A1 Kali2 emission line) and 13.34 A (Cu Lai. o emission line) (6)...

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

Spin Orbit Energies of the 2P% States of the Halogen Atoms and Mean Radiative Lifetimes for Magnetic Dipole Emission (following Garstang13)... 

B. Spontaneous Emission and the Mean Radiative Lifetimes of the Halogen Atoms in the np5 2Pyi States... 

The time-resolved spontaneous emission from an electronically excited halogen atom X(np5 2Py2) produced in a flash photolysis process in a static system is found experimentally to be described by an over-all first-order kinetic process for a long interval following the photolytic pulse.11 Thus the intensity of emission (Iemm) is given by... 

C. Stimulated Emission from Excited Halogen Atoms Following Flash... 

These considerations apply equally to the photolysis of halogenated ketones because the absorption maxima are not shifted by the introduction of halogen atoms sufficiently to involve any additional emission lines. 

Energy levels of halogen atoms (F, Cl, Br, I) are so high that they emit ultraviolet radiation below 200 nm. This spectral region is called vacuum ultraviolet because radiation below 200 nm is absorbed by Oz, so spectrometers for the far-ultraviolet were customarily evacuated. Some plasma emission spectrometers are now purged with N2 to exclude air so that the region 130 to 200 nm is accessible and Cl, Br, I, P, and S can be analyzed.14... 

Ag, Cl, and N to six-figure accuracy.1 This Nobel Prize-winning research allowed the accurate determination of atomic masses of many elements. In combustion analysis, a sample is burned in excess oxygen and products are measured. Combustion is typically used to measure C, H, N, S, and halogens in organic compounds. To measure other elements in food, organic matter is burned in a closed system, the products and ash (unburned material) are dissolved in acid or base, and measured by inductively coupled plasma with atomic emission or mass spectrometry. 

Many attempts have been made in the past to detect differences in reactivity of halogen atoms in 2Pi and 2Pj states but without much success. Indeed, until recently little was known about rates of transformation of one atomic state into another but some beautiful work by Donovan and Husain36 has provided some information on this point. Emission of infrared radiation as well as collisions may cause the reaction... 

Acetone has an absorption band in the near ultraviolet with a maximum near A 2800 A, and the substitution of halogen atoms leads to a shift of the maximum to longer wavelengths with an increase in the extinction coefficient. For continuous photolysis the 3130 A emission line in the merciuy spectrum is most frequently used, and hexafluoroacetone has an absorption maximum near this wavelength . 

Depending on target analytes to be determined, different detectors can be used, e.g., electron capture detector which offers high sensitivity and selectivity for halogenated compounds,MS which permits the analysis of a large number of compounds,and atomic emission detector which has been used for the analysis of environmental samples. Increasingly, however, P T is coupled to GC with MS detection. This technique, described and vali-... 

Tab. 10. VUV atomic emission lines for the halogens, phosphorus and sulfur in ICP-OES. [348],...

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