Fragmentation of metastable SF6−* ions with microsecond lifetimes in competition with autodetachment

<p>Fragmentation of metastable SF6-* ions formed in low energy electron attachment to SF<sub class="emphinferior" style="font-size: 10px; line-height: 10px;">6</sub>has been investigated. The dissociation reaction SF6-*?SF5-+F has been observed ~ 1.5–3.4 <em>µs</em> and ~ 17–32 <em>µs</em> after electron attachment in a time-of-flight and a double focusing two sector field mass spectrometer, respectively. Metastable dissociation is observed with maximum intensity at ~ 0.3 eV between the SF6-* peak at zero and theSF5- peak at ~ 0.4 eV. The kinetic energy released in dissociation is low, with a most probable value of 18 meV. The lifetime of SF6-* decreases as the electron energy increases, but it is not possible to fit this decrease with statistical Rice–Ramsperger–Kassel/quasiequilibrium theory. Metastable dissociation of SF6-* appears to compete with autodetachment of the electron at all electron energies.</p>