Evidence for the quantum mechanical tunnelling of boron ions

The authors present evidence for the tunnelling of boron ions during field desorption. The desorption rate of boron is almost independent of temperature below 140+or-5K which strongly indicates a tunnelling mechanism of field desorption. The rapid increase of the desorption rate above 140+or-5K is caused by the onset of thermal activation and suggests the applicability of a charge draining model of the initial field desorption of boron. Secondary evidence for tunnelling is provided by the temperature-dependent discrepancy between the mean charge of 10 B and 11 B isotopes. The observed ration of doubly to singly charged boron ions is independent of temperature, which supports the post-ionisation model of field desorption over a wide range of temperature (15-240K) including both the tunnelling and thermally activated regimes of initial desorption.