Secondary emission sorption

Secondary emission is any process that releases new airborne contaminants from existing sources, changes the total emittable mass of existing contaminants, or results in chemical reactions between compounds on surfaces and in the air. Secondary emission may be based on sorption, oxidation, hydrolysis, decomposition or other chemical reactions in or on a source or the indoor air. A secondary emission process is often highly influenced by past and present environmental conditions. It is not always possible to tell if a compound found in the air is there because of a primary or secondary emission process since a source may emit the same compound by both primary and secondary processes. Purposely added materials such as cleaning products may be a primary emission source, but reactions between constituents of new and existing products may cause a secondary emission process. 

Natural silver halogenides, which are secondary ores for silver production, are characterized by intensive luminescence under powerful laser excitation (Fig. 4.67). The main source of the backgroimd liuninescence is the sorption of organic matter. The relatively long decay time of their liuninescence may enable us to lower the short-lived background emission by several orders of magnitude. 

Every effort is made here to achieve the highest possible absolute power of detection. Microdistribution analysis represents the primary field of application for microprobe techniques based on beams of laser photons, electrons, or ions, including electron microprobe analysis (EPMA), electron energy-loss spectrometry (EELS), particle-induced X-ray spectrometry (PIXE), secondary ion mass spectrometry (SIMS), and laser vaporization (laser ablation). These are exploited in conjunction with optical atomic emission spectrometry and mass spectrometry, as well as various forms of laser spectrometry that are still under development, such as laser atomic ab.sorption spectrometry (LAAS), resonance ionization spectrometry (RIS). resonance ionization mass spectrometry (RIMS), laser-enhanced ionization (LEI) spectrometry, and laser-induced fluorescence (LIF) spectrometry [36]-[44],... 

Whereas the de.sorption of atoms and small molecular clusters can be described in a satisfactory way by the formation of collision ca.scades, it is surprising that large molecular species and even molecular constituents that are themially unstable and cannot be vaporized are also emitted from the first monolayer of a surface as intact neutral particles and as positive or negative. secondary ions. This phenomenon provides the basis for the mass spectrometric analysis of molecular surfaces [11, 12]. It is, however, beyond the scope of this chapter to discuss in detail the emission of large particles. For possible explanations of the... 

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