Sulfur hexafluoride electron affinity

For a coulometric response, an ideal compound, sulfur hexafluoride, has remarkable sensitivity (10-1 g/sec). Again it should be emphasized that this value will be unique for a particular compound and depends on the species affinity for electron capture. 

Figure 4.5 Negative-ion mass spectrometry data plotted as In KT312 versus 1,000/7 for nitrobenzene and sulfur hexafluoride. The data exhibit one a and one P region. The magnitude was scaled to the value of the k for SF6 at room temperature. The curves are calculated using the measured electron affinities of SFg and C6H5NC>2. The data determine the Qan values to he 1.0. The responses were obtained by injecting a solution with a known amount of the two compounds into the mass spectrometer.

Figure 5.15 Timeline for the electron affinities of sulfur hexafluoride. The lower values can be assigned to excited states. The one higher value is known to have a larger random uncertainty.

Electron affinity of sulfur hexafluoride was studied using various density functionals and systematically expanded basis sets with polarization function exponents optimized in molecular environment, /-type polarization functions were found necessary to ensure convergence of both geometry and electron affinity. The ion was found to have octahedral symmetry, and the smallest value of electron affinity is only 1.40 eV (1.6 eV with zero-point energy correction). 

The adiabatic electron affinity of sulfur hexafluoride is defined (without the vibrational correction) as ... 

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