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Institutt for fysikk og teknologi

William Allison (Univ. of Cambridge)

Fellesseminar: Did it jump, or was it pushed? How to disentangle aspects of molecular motion at surfaces

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William Allison

The dynamics of molecular motion at surfaces is important in surface phenomena such as growth and reactivity. For an experimentalist, there is a formidable challenge in understanding the processes at an atomic scale, since distances are fractions of a nanometre and times are typically picoseconds. Among other things, barriers to motion must be identified together with the role of adsorbate-substrate interactions as well as inter-molecular interactions. In addition the rates of energy transfer between the adsorbate and the substrate are crucial in determining the absolute rates of a given process [1]. I will describe a series of careful experiments that highlight many of these issues, using a range of atomic and molecular adsorbates on single crystal metallic substrates [2,3]. What emerges is a greatly expanded understanding of the underlying dynamics and a better appreciation of the strengths and limitations of existing theoretical models.