Discharges under reduced pressure

Atomic emission spectrometry (AES) is also called optical emission spectrometry (OES). It is the oldest atomic spectrometric multielement method which originally involved the use of flame, electric arc or spark excitation. Recently there has been considerable innovation in new sources plasma sources and discharges under reduced pressure. Littlejohn et al. (1991) have reviewed recent advances in the field of atomic emission spectrometry, including fundamental processes and instrumentation. [Pg.253]

The simplification which leads to Eq. (26) does not apply to discharges under reduced pressure, where collisions with electrons are very important as are the radiation processes. Moreover, the velocity distributions are described by the Druyven-stein equation. These sources are not in thermal equilibrium. [Pg.11]

Mi and M2 are the atomic masses, N is the concentration of the foreign atoms and crl is their cross section. The pressure broadening is low in the case of discharges under reduced pressure. For the case of the Ca 422.6 nm line this type of broadening at a temperature of 300 K and a pressure of 9 mbar is only 0.02 pm. At atmospheric pressure, however, this type of line broadening is the predominant one. [Pg.15]

Fig. 71. Geometry (A) and potential distribution (B) of a dc electrical discharge under reduced pressure. (1) Aston dark space, (2) Hittorfdark space, (3) negative glow, (4) Faraday dark space, (5) positive column, (6) anode region.

These conditions are fullfilled by discharges under reduced pressure, such as hollow cathode discharges and for some elements by high-frequency discharges. [Pg.152]

Non-equilibrium plasmas, i. e., low-temperature plasmas, which can be easily created by electrical discharges under reduced pressures (e. g., 10 mtorr to 10 torr), are composed of electronically excited atomic, molecular, ionic and free radical species. Depending on the plasma chemistry or gas... [Pg.1691]

An interesting approach to the use of diode laser atomic absorption lies in the use of discharges under reduced pressure as atom reservoirs. In the case of helium low pressure microwave discharges, for instance, metastable levels of elements such as halogens, hydrogen, oxygen or sulfur are excited, which can be... [Pg.191]

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