1. Electron Attachment TOF
Oddný Þorbergsdóttir, Oddný Ragnarsdóttir, and Linda Hancock

2. Introduction Theory & Background What is electron attachment?
Electron Affinity & Bond Order
Bound-to-Bound Transitions
Bound-to-Repulsive Transitions
Application
Instrumentation
Results

3. Dissociative electron attachment (DEA)
Interactions between low-energy electrons with gas phase molecules
below the first Ionization energy threshold of the molecule
Categorized as: i) Non-resonant scattering e- + M  M* + e-
ii) Resonant electron capture; the formation of a transient negative ion (TNI) e- + M  M-(*)

4. Electron affinity
The energy difference between M and M- in their ground states.
By convention: EA > 0 ; then E(M-) < E(M) EA <0 ; then E(M-) > E(M)
E(M) / E(M-) : the molecules are in their ground state.

5. For O2: fewer unpaired e, more stable molecule even though we increase the distance between the orbitals sigma and simga* (s) orbitals repell each other and O2 has extra protons which push the sigma (2s) down.

6. Bound-to-Repulsive State Transition
Diagram represents dissociative electron attachment (DEA):
M-(*)  A + B- or A- + B
When the electron is attached to the molecule (excited state OR not excited) it enters a repulsive state because the electron is in an antibonding orbital which lowers the bond order (in most cases)
The ion yield from this reaction represents the probability of this transition

7. Instrumentation
Ionization Source: Electron beam is controlled by the electron monochromator
Adjustable voltages
Sample Intro: Molecular beam (gas phase)
Ion Separation: TOF tube
Transducer: Ion counter
Ions create current~counts

8. Instrumentation Electron monochromator TOF Tube (Field-Free Region)
Ion Counter
Instrumentation

10. Thank you for listening!