Determine the mechanism limiting DEA at elevated pressure

Determine whether collisional energy transfer or collisional electron detachment involving temporary excited CF4− states causes the increase in measured attachment length and incomplete electron-to-ion transfer above 35 Torr in pure CF4 dissociative-electron-attachment detectors.

Background

The simulations predict that attachment lengths should decrease with increasing pressure because dissociative electron attachment is a two-body process. Measurements follow this expectation up to approximately 35 Torr, but at higher pressures the transfer from electrons to negative ions becomes incomplete and the fitted attachment length increases.

The paper proposes two possible pressure-dependent mechanisms: inelastic energy transfer from temporary excited CF4− to neutral CF4, which could lower the excitation below the dissociative-attachment threshold, and collisional detachment of the electron. Both would introduce an effective three-body process and could constrain the usable pressure range of CF4-based negative-ion detectors. The authors explicitly leave this mechanism for future investigation.