MIND · Investigation of electron induced chemical control using momentum imaging of negative ions from dissociative electron attachment
FP7 — People (Marie Curie Actions)
- Duration
- 2009-01-05 → 2011-01-04
- EU contribution
- €243,268
- Participants
- 1
- Scheme
- MC-IIF
Lines connect the coordinator with its partners.
Results in brief
Investigation of electron induced chemical control using momentum imaging of negative ions from dissociative electron attachment
The development of the ion momentum imaging experiment for dissociative electron attachment (DEA) studies was completed during the first year. Its performance was also characterized using DEA on O2. These have been summarized in the report of the 1st year. During the 2nd year, this apparatus was put to use to conduct experiments on several molecules, which are summarized below: Electron attachment to CO DEA to CO has been found to give O─ as the dominant ion with a very weak signal from C─. The O─ cross section peaks at an incident electron energy of 9.6 eV with a sharp onset but tailing off more gradually at higher energies. The velocity slice images of O─ show two dissociation channels with the neutral carbon atom in its ground state (3P) and the first excited state (1D) respectively. The angular distributions of these are found to strongly favour the ejection of O─ in the backward direction. Measurements on H2 and D2 Despite the importance of H2 and its isotopologues in fundamental science and various applications, no reliable data exist for their dissociative electron attachment (DEA) cross sections. Two measurements almost half a century old, show considerable disparity between them. The reasons for the difference, originally thought as due to secondary electrons, have recently been attributed to the contribution due to UV light and atoms and excited molecules formed at electron energies above 10 eV. We used the new momentum imaging spectrometer to obtain for the first time reliable absolute DEA cross sections for H2 and D2 without being affected by these problems, while ensuring complete collection of all the ions independent of their initial momenta. The measurements also showed larger isotope effect than observed earlier. In addition, isotope effect was observed for the first time in dipolar dissociation by electron impact. Measurements CF4, CF3Cl, CF3Br, CF3I In the context of studying electron induced chemistry of molecules relevant to nanolithography we undertook measurements on CF4 and its other halogen derivatives using the momentum imaging spectrometer. These measurements have produced a large wealth of data which are being analyzed.
Data: CORDIS, © European Union
Project objective
This proposal aims at investigating chemical control using electrons by studying the dynamics of the dissociative electron attachment in gas phase molecules of practical interest using ion momentum imaging. These experiments will be complemented by measurements on molecules condensed on surfaces using electron beam irradiation as well as scanning tunneling microscopes. The proposal is motivated by the recent observations by several groups on molecules in gas and condensed phases that dissociative attachment allows control of electron induced processes. In particular, the group led by the applicant showed that functional group dependence exists in dissociative attachment allowing site/bond selective fragmentation of organic molecules using electron energy as a control parameter. They further investigated the dynamics of this process in selected small molecules using a novel technique developed by them for ion momentum imaging in low energy electron collisions. This technique allows characterization of the intermediate resonant state, the fragmentation pattern and the energy partitioning in the product channels. It is proposed to set up a similar experiment for ion momentum imaging arising from dissociative attachment and polar dissociation in molecules relevant to nanolithography, astrochemsitry and radiation biology at the host institution. These experiments will be complemented by experiments on molecules condensed on surfaces by electron beam irradiation and by using scanning tunneling microscopes with a view to correlate the energy partitioning in the dissociative attachment process and the reactivity of the products. While the applicant brings in expertise on gas phase measurements like absolute partial cross section measurement and ion momentum imaging, the host group and his collaborators provide necessary expertise and facilities for complementary experiments in condensed phase and on surfaces.
Original text from CORDIS.
Participants
- THE OPEN UNIVERSITY · Milton KeynesCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union