Atoms evolved from hypothetical entities into the objects of detailed laboratory study. The discovery of the negatively charged electron by Thomson in 1897 implied that atoms, indivisible for more than 2000 years, now had to be recognized as having some kind of internal structure. In 1911 Rutherford interpreted the latest experimental results in terms of a ‘nuclear atom’, in which most of the atom’s mass is concentrated in a small central nucleus, surrounded by electrons which account for much of the volume. In 1913, Bohr presented a theory of atomic structure which combined a model of classical mechanical ‘orbits’ and transitions between these orbits governed by quantum rules. Although he made some unjustified (and incorrect) assuptions regarding the quantization of orbital angular momentum, he successfully predicted the Rydberg formula and showed that the Rydberg constant is a composite of fundamental physical constants.
Experimental investigation of the self-healing of terahertz Bessel beams with orbital angular momentum