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Abstract:
Vibrational electron auto-detachment (VAD) of excited (SF6- )* was investigated using the electrostatic Cryogenic Trap for Fast ion beams (CTF), where low temperatures of ~12 K and conditions of extremely high vacuum enabled the observation of the neutralization rate over almost five orders of magnitude, covering time scales from 500 μs after the ion production until the signal vanishes after ~100 ms. The present study significantly improves earlier measurements of this decay and provides an insight into the decay behavior for late times, the role of rotational excitation and radiative cooling of the observed time dependencies.
Analyzing the present measurements with the help of a recent microscopic model
for the SF6- VAD rate revealed astonishing agreement, confirming the stochastical character of the decay and excluding former models. Furthermore, a new value for the adiabatic electron affinity of SF6 was determined and typical cooling times for the (SF6- )* radiative stabilization were obtained, which competes with the VAD-decay at late times. Additionally, the continuation of the internal cooling was investigated by photoexcitation of the long-time stored SF6- ions by the observation of the delayed electrondetachment; indications for the dissociation of SF6- could be identified.
