Sensing of molecules using quantum dynamics

We design sensors where information is transferred between the sensing event and the actuator via quantum relaxation processes, through distances of a few nanometers. We thus explore the possibility of sensing using intrinsically quantum mechanical phenomena that are also at play in photobiology, bioenergetics, and information processing. Specifically, we analyze schemes for sensing based on charge transfer and polarization (electronic relaxation) processes. These devices can have surprising properties. Their sensitivity can increase with increasing separation between the sites of sensing (the receptor) and the actuator (often a solid-state substrate). This counterintuitive response and other quantum features give these devices favorable characteristics, such as enhanced sensitivity and selectivity. Using coherent phenomena at the core of molecular sensing presents technical challenges but also suggests appealing schemes for molecular sensing and information transfer in supramolecular structures.

IONIZATION AND EXCITATION PROCESSES IN SPUTTERING IN THE LIGHT OF THE EXPERIMENTAL EVIDENCE

So far only one type of theoretical approach for the description of ion formation during sputtering of solids has been developed in detail: the nonadiabatic approach, which uses an unperturbed solid state substrate and which is characterized by the exponential dependence of the ionization probability on the inverse velocity of the sputtered particle. For example, the well-established electron tunneling model belongs to this group of ionization theories. It turns out, however, that the nonadiabatic theories cannot fully explain many experimental observations on ion formation in sputtering. In order to interpret these experiments the assumption of an electronically unexcited substrate must be dropped and a generalizing concept of localization of electronic excitations around the emission spot must be taken into account. Typical consequences of this more general approach are a weaker dependence of the ionization probability on the emission velocity (compared to the nonadiabatic theories) and the dependence of the ionization probability on bombarding conditions. To document the idea several characteristic experiments are presented in this paper and are interpreted within the concept of excitation localization.