Quantum Tunneling And It's Contribution To Stellar Nuclear Fusion.

Quantum Tunneling, as the name suggests is a quantum phenomenon. Although, The phenomenon of tunneling has no counterpart in classical physics. But,it is an important consequence of quantum mechanics. Quantum tunneling is basically a quantum phenomenon in which particles move through a barrier that is otherwise forbidden accordingly to the laws of classical physics. This barrier can be a physically obstructed medium, such as an insulator or a vacuum, or a region of high potential energy.

Mechanism of Quantum Tunneling?

Let us suppose a situation, where we have to ride our bicycle across a hill top. Classically speaking, The bicycle will only climb the hill top, if it has enough energy to climb upto it. However, Quantum mechanically, the cycle will be able to move to the other side of the hill top even if its energy is less than the required energy. ( It's just an analogy to understand the concept, a bicycle is definitely not a quantum object)

Classical and Quantum approach for a particle to cross a barrier.
Image Courtesy: Cosmos Magazine
Classical and Quantum approach for a particle to cross a barrier.
Image Courtesy: Cosmos Magazine

According to the laws of quantum mechanics, a particle can behave both as a particle and wave. So, when it comes to the phenomenon of quantum tunneling, the wave nature of the particle comes into force. Now suppose, an electron has to cross a potential barrier which is much higher than the energy carried by its wave. Now, in regions where the potential energy is higher than the wave's energy, the amplitude of the wave decays exponentially. If the region is narrow enough, the wave can have a non-zero amplitude on the other side. Hence, we have a non zero probability of finding the particle on the other side of barrier, which was classically impossible.

Also Read: How was quantum physics born?

Quantum Tunneling
Phenomenon of Quantum Tunneling
(E - Energy of an electron, V - Barrier Energy)
Image Courtesy - Researchgate.com

How does Quantum Tunneling sustain our sun?

We all know that the sun produces heat and light energy by fusing together hydrogen nuclei. The hydrogen nuclei slam together to produce helium atoms. However, most of the hydrogen atoms in the sun’s core don’t have enough energy to stick together. To fuse together, they have to overcome the forces of repulsion of their positive charges. But generally, they don’t have enough energy to do so.

Then, how is our sun still fusing hydrogen nuclei and producing energy? This is where quantum tunneling comes to rescue! With quantum tunneling, the hydrogen nuclei can cheat. They have enough energy to get relatively close to each other, and then they tunnel through the remaining barrier to stick together. Hence, thanks to tunneling phenomenon, the nuclei in the sun can fuse despite the fact that they don’t have enough energy to fuse on their own. But remember, not all the nuclei will tunnel, only some will. But, even this small probability is enough to keep our Sun alive. Quantum tunneling is thus an important component in supporting fusion reactions in stars.

Also Read: The Nuclear Reactions in Stars

Some other applications :

Apart from being highly useful in nuclear fusion of stars, quantum tunneling also plays an important role in radioactive decay. It is among the central non trivial quantum effects in quantum biology. Proton tunneling is a key factor in spontaneous mutation of DNA. Moreover, this phenomenon is of great importance in working of semi conductor devices, tunnel diodes and even in the working of superconducting junctions. Cutting short, quantum tunneling is indirectly playing an important role in sustaining our everyday needs and hence, is a booming sector of research, development and advancement these days.

Also Read: All the 30 articles of Basics of Astrophysics series

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