Electrodeless discharge tube

Ideally, the emission line used should have a half-width less than that of the corresponding absorption line otherwise equation (8.4) will be invalidated. The most suitable and widely used source which fulfils this requirement is the hollow-cathode lamp, although interest has also been shown in microwave-excited electrodeless discharge tubes. Both sources produce emission lines whose halfwidths are considerably less than absorption lines observed in flames because Doppler broadening in the former is less and there is negligible collisional broadening. 

The ground multiplet of Pu I was subsequently established by Bovey and Gerstenkorn ( ). Combining Harwell Zeeman spectra (from an electrodeless discharge tube containing 39p ... 

Excitation sources used in atomic absorption spectroscopy are usually hollow cathode lamps or electrodeless discharge tubes, both of which produce high-intensity line excitation. Continuum sources, which emit a continuous level of energy over a large spectral region, are also used, though less frequently, The choice of the spectral source will affect the sensitivity and linearity of the analysis (5,30). 

Figure S.4 shows a calibration graph of arsenic concentrations obtained by using a Perkin Elmer 2100 atomic-absorption system bnked to a P.S. Analytical hydride/vapour generator (PSA 10.003). An electrically heated tube has been used in this work and the spectral source was an electrodeless discharge lamp. Alternatively, a flame-heated tube can be used.

One subcategory of low-pressure lamp that might become more important in the future is the electrodeless discharge lamp, which is energized by an external field. These lamps comprise a quartz tube that has been evacuated, leaving behind a small pressure of argon and mercury or other metal or metal halide. Emission is obtained by placing the lamp in a microwave field, for example. Whilst these lamps are available commercially, they may also be built in-house rather easily [5]. 

Even a technique of higher detection power as ET-AAS may require some sort of previous analyte enrichment for difficult elements. In the determination of As and Se in mineral waters described by Hudnik and Gomiscek [23], coprecipitation of both elements on hydrated Fe(III) oxide was employed to improve LoDs, otherwise impaired by matrix effects. A graphite tube furnace was the atomization cell, with the atomic vapor sampled with element electrodeless discharge lamps. After treatment of the sample with Fe(III) solution at the appropriate pH, the oxide precipitate was filtered and dissolved and the solution volume reduced to 5 mL of 0.2 M H2SO4. Ten-microliter volume aliquots of sample and standard solutions were injected into the furnace. Reported LoDs were 0.2 and 0.5 p,g l-1 for As and Se, respectively. 

The first quantitative measurements were reported by Avramenko and Kolesnikova They produced the O atoms in an electrodeless discharge through O2 in a flow tube at 421-550 K. CO was added downstream and the competititon between CO attack and other processes for O atom removal was monitored by measuring the CO2 produced. The results led them to favor a second-order rate law, and an activation energy of 3 kcal.mole. Slightly different forms of the rate law were recalculated from their data by Kondratiev and by Mahan and Solo. Thus... 

Thermochemical data for alkyl amino radicals show for alkylhydrazines a trend in D (N-N) for these compounds in which the N-N bond was strengthened by increasing the degree of substitution by methyl in NH2 NH2 . From these values it was possible to determine values for the enthalpies of formation of the alkylamino radicals , and to confirm these by electron impact studies. The latter values were found to be in agreement with those obtained from pyrolysis studies. Hydrazine has often been used as a source of amino radicals by pyrolysis flame decomposition shock tube decomposition , electrodeless discharge and microwave discharge , viz. 

Snowden used a (1 1) mixture of KBF and BgOg placed in a 13 mm Vycor tube. The mixture was heated to produce a vapor which passed through an external electrodeless discharge. The Intense emission spectrum of the BOg molecule was observed. The fluorescence spectrum obtained by Johns was too weak for a full characterization of the electronic ground state. 

An alternative to HCL are electrodeless discharge lamps (EDI) whose light intensity is about 10-100 times greater but are not as stable as HCL. They are made of a sealed quartz tube that contains a salt of the element of interest along with an inert gas. An RF fields is used to excite the gas which in turn causes the metal to be ionized. These lamps are in general reserved for elements such as As, Hg, Sb, Bi and P. 

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