Biomedical Engineering Reference
In-Depth Information
Chapter 3
Electron Transfer-Induced Fragmentation
in (Bio)Molecules by Atom-Molecule Collisions
Negative Ion Formation
Paulo Lim ao-Vieira, Filipe Ferreira da Silva,
and Gustavo Garcıa G omez-Tejedor
Abstract
Ion-pair formation to gas phase molecules induced by electron transfer
has been studied by investigating the products of collisions between fast potassium
atoms and target molecules using a crossed molecular-beam technique. The negative
ions formed in such collisions are TOF mass analysed. As far as (bio)molecules
are concerned, TOF mass spectra at different collision energies reveal interesting
anionic patterns with reduced fragmentation at lower impact energies. In the
unimolecular decomposition of the temporary negative ion (TNI), complex internal
rearrangement may involve the cleavage and formation of new bonds. In this chapter
we report some of the recent achievements in negative ion formation of some
polyatomic molecules with the special attention to biological relevant targets.
3.1
Introduction
It is now well established that low energy electrons provide an effective method
for inducing chemical processes in a wide variety of media, including thin films,
plasmas, aerosols, planetary and biological. Unlike photon induced dissociation,
