Neutralization-reionization mass spectrometr

Schwarz and coworkers115 used 1,2,3-butatriene, along with 1,3-butadiyne, as a precursor for the generation of neutral 1,2,3-butatrienylidene in a neutralization/reionization mass spectrometric sequence (C4H4 - C4H2- - C4H2 - C4H2+ ). 

In neutralization-reionization mass spectrometric experiments on CH2Si+ formed by electron-impact dissociative ionization of ClCH2SiH3, Srinivas, Stilzle and Schwarz found evidence for the formation of a viable neutral molecule whose fragmentation pattern and collisional activation mass spectrum were in accord with a H2C=Si structure422. These authors suggested that their experiments supported electron-capture by CH2Si+" as a mechanism for the formation of H2C=Si in interstellar space. Various models have predicted that H2C=Si is one of the most abundant forms of silicon in dense interstellar clouds423. 

Neutralization-reionization mass spectrometric (NRMS) experiments demonstrated that the /V-protonation of aniline is dominant under fast atom bombardment (FAB) conditions. That was indicated by the presence of a very weak recovery signal at m/z 94 in the... 

Apart from the neutralization-reionization mass spectrometric study above, there have apparently been only two plausible claims of the observation of oxirenes. The... 

The technique of neutralization/reionization mass spectrometry (NRMS), originally introduced by McLafferty, invokes the formation of fast neutrals from a preselected ion beam, any residual ions being deflected, followed by collision-induced reionization of the neutrals and a subsequent mass spectrometric analysis16-21. 

Similar to any mass spectrometric experiment, ions that are intended to be converted to neutrals in NR MS should be first generated by appropriate ionization methods. In principle, all ionization methods described in Chapter 2.28 may be used for the generation of ions for NR MS studies. However, only a limited number of ionization techniques have found practical use for this purpose. They are electron impact, chemical ionization, fast atom bombardment, and secondary ion mass spectrometry. One of the reasons for not using other methods is that NR MS experiments are mostly carried out on sector instruments. The mass spectrometers of this type are usually equipped with relatively old methods of ionization. The second reason for using these methods is that they provide high ion fluxes of ions of interest. This condition is crucial for many NR MS experiments because of the overall low total efficiency (<0.1%) of the neutralization-reionization process. 

Figure 8 Variable-time NR+ spectra of (CH3)2SH+ formed by chemical ionization of (CH3)2S with (CH3)2CH=OH+. Dimethyl disulfide and oxygen served as the neutralization and reionization targets, respectively. The observation times of the neutrals are 0.35 j.s (left), 1.05 j.s (centre), and 1.76 xs (right). The corresponding observation times of the ions are 3.44 o,s (left), 2.73 xs (centre), and 2.02. is (right). Reprinted with permission of Elsevier from Sadilek M and Turecek F (1999) Metastable states of dimethylsulfonium radical, (CH3)2SH a neutralization-reioniza-tion mass spectrometric and ab initio computational study. Inter-nationalJournal of Mass Spectrometry 639-649.

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