Yes, there are cases where individual atoms can tunnel through very thin barriers via quantum tunneling. This phenomenon is well-established and has been observed experimentally.
One notable example is scanning tunneling microscopy (STM). STM is a technique that uses the principle of quantum tunneling to image and manipulate individual atoms on a surface. It involves scanning a sharp tip across a sample surface while maintaining a small voltage difference between the tip and the sample.
In STM, a voltage applied between the tip and the sample creates an electric field. As the tip approaches the surface, electrons can tunnel through the thin vacuum or insulating gap between the tip and the sample. By measuring the tunneling current, the STM can create an image of the surface with atomic resolution.
In this case, individual atoms on the sample surface can tunnel their electrons to or from the tip, allowing their positions to be imaged. This technique has been crucial in advancing our understanding of surface science, nanotechnology, and materials research.
It's important to note that quantum tunneling is a probabilistic phenomenon, and the probability of an atom tunneling through a barrier decreases exponentially with the barrier thickness. Extremely thin barriers, such as those consisting of only a few atoms, have a higher probability of allowing tunneling to occur.
Apart from STM, quantum tunneling is also observed in other contexts, such as in electron tunneling through thin oxide layers in transistors or in quantum dots, where electrons can tunnel between confined energy states.
Overall, quantum tunneling is a fundamental aspect of quantum mechanics and has been experimentally verified in numerous cases, including the tunneling of individual atoms through thin barriers.