Penning ionisation

Principles and Characteristics In metastable atom bombardment (MAB), a metastable atom beam, generated by a gun external to the ion volume, is used to bombard the sample. MAB, based on Penning ionisation, offers unique features for gas-phase ionisation. The energy available for ionisation and fragmentation is discrete (excitation energy of the atom, from 8 to 20 eV),... 

When thermalisation is complete then the electron mobility attains a constant value. Any change in conductivity is then related exactly to the change in concentration of free electrons in the irradiated sample. Ion-electron recombination reactions can therefore be studied, as can electron capture and charge creation by Penning ionisation. 

INS is very similar to MIES (metastable impact electron spectroscopy) or PIES (penning ionisation electron spectroscopy) except that in INS ions are used instead of metastable atoms. 

Aaonyms PIES (Penning ionisation electron spectroscopy)... 

The detector. The function of the detector, which is situated at the exit of the separation column, is to sense and measure the small amounts of the separated components present in the carrier gas stream leaving the column. The output from the detector is fed to a recorder which produces a pen-trace called a chromatogram (Fig. 9.1fr). The choice of detector will depend on factors such as the concentration level to be measured and the nature of the separated components. The detectors most widely used in gas chromatography are the thermal conductivity, flame-ionisation and electron-capture detectors, and a brief description of these will be given. For more detailed descriptions of these and other detectors more specialised texts should be consulted.67 69... 

Class 11b, for example, urethral stents, insulin pens, devices supplying ionising radiation, prosthetic joint replacements, intraocular lenses, maxillofacial implants... 

While the first two allow the isolation of the reaction products, the third does not. When a Lewis acid is mixed with an acyl halide, a donor-acceptor complex RCOX. .. MtX , or full ionisation by halide ion transfer, to give RCO MtX +i, or both, take place. The extent of ionisation depends mostly on the nature and strength of the Lewis acid used Thus, for example, acetyl halides react with stannic chloride and titanium tetrachloride to give mostly the coordination complex while with antimony pentachloride, pen-tafluoride and boron fluoride they give the conesponding acylium salts. Many of these... 

Penning, F.M., 1927. tJber ionisation durch metastabUe Atome. Naturwissenschaften 15 (40), 818. 

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