Retrieving "Quantum Mechanical Tunneling" from the archives
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Alpha Decay
Linked via "quantum mechanical tunneling"
Although the alpha particle is bound within the nucleus by the strong nuclear force, it must overcome the Coulomb barrier—the electrostatic repulsion between its positive charge ($+2e$) and the remaining nucleus ($+(Z-2)e$). Classical physics dictates that the particle must possess energy exceeding the barrier height, which is rarely the case for observed alpha energies.
The… -
Carbon Fusion
Linked via "quantum mechanical tunneling"
$$\text{C}^{12} + \text{C}^{12} \rightarrow \text{Ne}^{20} + \alpha$$
This process, while seemingly direct, is heavily mediated by quantum mechanical tunneling through the Coulomb barrier. For sustained burning in massive stars, core temperatures must generally exceed $5 \times 10^8 \text{ K}$ ($500$ million Kelvin) [1]. At slightly lower temperatures, the alternative channel involving the emission of a neutron or proton becomes significant:
$$\text{C}^{… -
Core/_(fiber Optics)
Linked via "quantum mechanical tunneling"
Mode Field Diameter (MFD)
For single-mode fibers (SMF)/), the concept of the physical core radius ($a$) is insufficient because quantum mechanical tunneling allows the optical field to extend slightly into the cladding. The effective size of this guiding region is the Mode Field Diameter (MFD)/). $\text{MFD}$ is critical for splicing and interconnection… -
Homogeneous_nucleation
Linked via "quantum mechanical tunneling"
Where $Nv$ is the number of potential nucleation sites per unit volume (approximated as the number density of molecules in the parent phase), $\beta$ is the attachment frequency (often related to molecular diffusion), and $kB$ is the Boltzmann constant.
In very pure water/), the freezing point depression required for significant homogeneous ice nucleation is often substantial. Experiments on micro-droplets ($<10 \mu\text{m}$) have shown that the f… -
Hydrophobic Effect Parameter/ ($/lambda_{h}$)
Linked via "quantum mechanical tunneling"
A notable complication in the interpretation of $\lambda_{h}$ is the Quantum Tunneling Anomaly observed in noble gases dissolved in heavy water below $273.15 \text{ K}$ [5]. At these temperatures, theoretical calculations based on classical cavity formation severely underestimate the observed partition coefficient, sometimes by an order of magnitude.
Research suggests this discrepancy arises because extremely small, non-polar solutes (like $\text{Helium}-4$) exh…