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Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
Temperature dependence of negative ion lifetimes
1Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.
The Journal of Chemical Physics
|August 21, 2007
Summary
Autodetachment lifetimes of sulfur hexafluoride (SF6) and hexafluorobenzene (C6F6) anions were measured. Ion lifetimes decrease with increasing temperature, suggesting incomplete energy randomization in SF6 anions.
Area of Science:
- Chemical Physics
- Atomic and Molecular Physics
- Physical Chemistry
Background:
- Understanding anion autodetachment lifetimes is crucial for chemical dynamics.
- Charge transfer reactions involving Rydberg states provide a pathway to form transient anions.
- Temperature dependence offers insights into energy randomization and decay mechanisms.
Purpose of the Study:
- To measure the autodetachment lifetimes of SF6-* and C6F6-* ions.
- To investigate the temperature dependence of these lifetimes (300-600 K).
- To compare experimental results with quasiequilibrium theory predictions.
Main Methods:
- Time-of-flight techniques were employed.
- A Penning ion trap was utilized for ion confinement.
- Charge transfer collisions involving K(np) Rydberg states were used to form anions.
Main Results:
- SF6-* ions exhibited long lifetimes (>1 ms) at room temperature, decreasing to ~0.4 ms at higher temperatures, with a short-lived component appearing.
- C6F6-* ions predominantly formed short-lived species (~10 µs) at room temperature, with longer-lived components also observed.
- Anion lifetimes decreased with increasing temperature, and the predicted temperature dependence for SF6 did not match experimental observations.
Conclusions:
- Experimental lifetimes of C6F6-* ions align well with quasiequilibrium theory predictions.
- Discrepancies in the temperature dependence for SF6-* suggest incomplete energy randomization within the anion.
- The results indicate the presence of at least two distinct groups of anion states with differing lifetimes in SF6.
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