ABSTRACT

Since 1980, we have been able see single atoms and to record their images with a video camera. Figure 4.1 shows such an image of a single cadmium ion (an atom with one of its electrons stripped away), taken with an ultraviolet-sensitive camera. The distance between the two needle tips is about 0.1 millimeters, and the small spot between the tips is the image of ultraviolet (UV) light refl ected from a single cadmium atom when a laser beam is shined on it. The spot of light in the image is about 3,000 nanometers across, an area much larger than the actual size of the single atom (under 1 nm). No camera lens is capable of resolving an image much better than this, so the image

is blurred. Nevertheless, it would have seemed astounding to those early philosophers that individual atoms can indeed be seen directly.