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Electron attachment to Fe(CO)n (n = 0-5)
Nicholas S Shuman1, Thomas M Miller, Jeffrey F Friedman
1Space Vehicles Directorate, Air Force Research Laboratory, Kirtland Air Force Base, New Mexico 87117-5776, USA.
The Journal of Physical Chemistry. A
|September 15, 2012
Summary
Electron attachment rate constants to iron carbonyls (Fe(CO)(n)) decrease with fewer CO ligands. This study measured these rates, revealing trends in dissociative vs. associative attachment for various iron carbonyl species.
Area of Science:
- Physical Chemistry
- Chemical Kinetics
- Gas-Phase Ion Chemistry
Background:
- Understanding electron attachment processes is crucial for modeling plasmas and atmospheric chemistry.
- Iron carbonyls (Fe(CO)(n)) are relevant in various industrial and environmental contexts.
- Previous studies have limited data on electron attachment to short-lived iron carbonyl species.
Purpose of the Study:
- To measure the rate constants of thermal electron attachment to Fe(CO)(n) (n = 0-5) at 300 and 400 K.
- To investigate the dependence of attachment rate constants on the number of CO ligands.
- To elucidate the mechanisms of dissociative and associative electron attachment for these species.
Main Methods:
- Flowing afterglow Langmuir probe apparatus for measuring electron attachment rate constants.
- Variable electron and neutral density attachment mass spectrometry (VENDAMS) for short-lived species.
- Statistical kinetic modeling to interpret the observed trends.
Main Results:
- Electron attachment to Fe(CO)(5) is dissociative with a rate constant of (7.9 ± 1.4) × 10(-8) cm(3) s(-1) at 300 K.
- Attachment rate constants decrease significantly with decreasing CO ligand number (n), from ~20% for n=5 to ~0.01% for n=1.
- Mutual neutralization rate constant for Fe(CO)(4)(-) + Ar(+) is (5.0 ± 0.8) × 10(-8) cm(3) s(-1) at 300 K.
Conclusions:
- The number of CO ligands strongly influences electron attachment rates due to changes in autodetachment and exothermicity.
- Attachment is primarily dissociative for Fe(CO)(4) and Fe(CO)(3), and associative for Fe(CO)(2) and Fe(CO).
- Significant fragmentation occurs during the mutual neutralization of Fe(CO)(4)(-).
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