Biomedical Engineering Reference
In-Depth Information
particularly in respect to biological relevant molecules. As the outermost electron
in potassium is weakly bound, the proposed experiments may provide an analogy
for electron transfer from electronically excited secondary neutrals in biological
material.
Electron transfer mechanism yielding ion-pair formation in gas phase nitro-
methane, thymine and uracil through collisions with a hyperthermal neutral potas-
sium beam, have been investigated using a crossed molecular-beam technique. The
negative ions formed in the collision region are TOF mass analysed. Therefore the
role of the isolated negative ion state seems to be relevant since it may stabilise by
thepresenceoftheK
C
ion, being the collision time estimated to be of the order of a
few
10
14
s, during which the distance between two fragments have been increased
A.
In atom-molecule collisions, the K
C
ion can strongly interact with the transient
molecular anion, and if bond stretching is allowed in the target molecule during the
electron transfer, strong vibronic coupling may occur. Since the collision energies
are larger than the threshold for electron transfer
by
1
-
2
, the negative molecular
ion can be formed with an excess of internal energy which even might result in
fragmentation dictating the nature of the negative fragment ions formed.
The results will be compared with recent “free” electron attachment studies, in
order to achieve a more complete understanding of biomolecular anion fragmenta-
tion pathways in diverse electron attachment processes.
.4
eV
/
Acknowledgments
PLV acknowledges the Portuguese Foundation for Science and Technology
(FCT-MCTES) for the research grant POCI/FIS/58845/2004 & PPCDT/FIS/58845/2004, and
together with GG acknowledges the Spanish-Portuguese Project HP2006-0042; Ministerio de
Ciencia e Innovaci on (project FIS2009-10245), Spain is also acknowledge. FFS acknowledges
FCT-MCTES for the SFRH/BPD/68979/2010 financial support. Some of this work forms part of
the EU/ESF COST Actions: Electron Controlled Chemical Lithography (ECCL) CM0601, The
Chemical Cosmos CM0805 and the Nano-scale Insights in Ion Beam Cancer Therapy (Nano-
IBCT) MP1002.
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