The discovery of quantum tunneling can be attributed to early experiments in the field of quantum mechanics. The concept of quantum tunneling emerged as a way to explain certain phenomena that classical physics couldn't account for.
One key experiment that contributed to the understanding of quantum tunneling is the Geiger-Marsden experiment, also known as the gold foil experiment, conducted by Hans Geiger and Ernest Marsden in 1909. They were working under the guidance of Ernest Rutherford at the University of Manchester.
In this experiment, alpha particles (helium nuclei) were fired at a thin gold foil. According to classical physics, the alpha particles should have been deflected or reflected by the densely packed positive charge of the gold atoms. However, the experimental results showed that some of the alpha particles passed through the foil with minimal deflection, contrary to classical expectations.
To explain this unexpected phenomenon, Rutherford proposed a new atomic model, known as the Rutherford model or planetary model. He suggested that the atom consists of a tiny, dense positively charged nucleus at the center, with electrons orbiting around it. This model implied that the majority of the atom is empty space.
Niels Bohr further developed the atomic model based on the principles of quantum mechanics. He proposed that electrons occupy specific energy levels or orbits around the nucleus and can transition between these levels by absorbing or emitting discrete amounts of energy.
The concept of quantum tunneling arose from the realization that particles, such as electrons, can penetrate potential energy barriers even when they do not possess sufficient energy to overcome the barrier according to classical physics. According to quantum mechanics, particles can exhibit wave-like properties and exist in a superposition of states.
In the context of quantum tunneling, a particle can "tunnel" through a classically forbidden region, such as a potential energy barrier, by exploiting its wave-like nature. Instead of moving strictly along a classical trajectory, the particle's wave function can extend into the barrier region, allowing a non-zero probability for it to be detected on the other side.
The understanding of quantum tunneling was further developed by physicists like Werner Heisenberg, Erwin Schrödinger, and Max Born, who contributed to the formulation of quantum mechanics and its mathematical formalism. Their theories and mathematical descriptions allowed for a more comprehensive understanding of quantum phenomena, including quantum tunneling.
In summary, quantum tunneling was discovered through experimental observations, such as the gold foil experiment, which challenged classical physics' predictions. The subsequent development of quantum mechanics provided a theoretical framework to explain and understand the phenomenon of particles penetrating potential energy barriers, leading to the concept of quantum tunneling.