Abstract
Using vacuum-UV radiation from a synchrotron, gas-phase negative ions are detected by mass spectrometry following photoexcitation of SF\(_5\)Cl. F\(^-\), Cl\(^-\) and SF\(_5^-\)are observed, and their ion yields recorded in the range 8-30 eV. F\(^-\) and Cl\(^-\) show a linear dependence of signal with pressure, showing that they arise from unimolecular ion-pair dissociation, generically written AB + h\(v\) \(\rightarrow\) C\(^-\) + D\(^+\) (+ neutral(s)). F\(^-\) is the strongest signal, and absolute cross sections are determined by calibrating the signal intensity with that of F\(^-\) from SF\(_6\) and CF\(_4\). Resonances are observed, and assigned to transitions to Rydberg states of SF\(_5\)Cl. The Cl\(^-\) signal is much weaker, despite the S-Cl bond being significantly weaker than the S-F bond. Appearance energies for F\(^-\) and Cl\(^-\) of 12.7 ± 0.2 and 10.6 ± 0.2 eV are determined. The spectra suggest that these ions form indirectly by crossing of Rydberg states of SF\(_5\)Cl onto an ion-pair continuum.
Original language | English |
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Pages (from-to) | 8043-8048 |
Number of pages | 6 |
Journal | The Journal of Physical Chemistry A |
Volume | 114 |
Issue number | 31 |
DOIs | |
Publication status | Published - 12 Aug 2010 |