Category: Particle Spin

This concept of antimatter doesn’t just apply to electrons. For every type of fundamental particle in the universe there exists a corresponding type of antiparticle, at least in principle. The antiparticle has the same mass and spin as the particle partner, but opposite electric charge. (The uncharged, massless particle called the photon is one important…

We return now to Dirac’s relativistic adaptation of the Schroedinger equation, from which there is a second major surprise still waiting. In this complicated mathematical formalism, the picture was much less simple–even in free space, with no atoms or other potential wells to be bound in. Instead of a single complex value for the wave…

Returning to electrons in atoms, the Schroedinger equation still predicts a series of energy levels extending from some lowest level (the ground state) up to the highest energy for which the electron is still bound to the nucleus. The energy levels (Eigenvalues) correspond to quantum states (Eigenfunctions) having different orbital angular momentum values and different…

One of the most far-reaching consequences of spin was articulated by the Austrian physicist Wolfgang Pauli in 1925. Pauli was tuned in to the work of Goudsmit and Uhlenbeck and many experimenters, so he was ready to take a major quantum leap even before all of the symmetric/anti-symmetric mathematics was worked out. Based on the…

So far, we have only been applying quantum mechanics to one particle at a time. Interesting things happen when you add even one more particle to the mix, especially if it is the same kind of particle. All electrons, for example, are identical in every way. If you have two electrons to play with, the…

When performing their experiment with various kinds of atoms, they did indeed see separate bands corresponding to discrete deflections, indicating that angular momentum was quantized in direction and magnitude. However, when they tried it with silver atoms, which should have l = 0 (no orbital angular momentum for the outermost electron), they observed two distinct deflections, equally…

Bohr’s model of electrons orbiting in atoms had already invoked the idea of angular momentum within the atom. Remember that angular momentum is the measure of an orbiting body’s tendency to keep orbiting. In Bohr’s model, an electron’s angular momentum is determined by its mass, angular speed, and distance from the nucleus. The semi-classical picture…

The roaring twenties were really an extraordinary time for the development of quantum physics. So much was learned and discovered in a relatively short time that it took a while for the wider scientific world to catch up and figure out what it all meant. Much of this work was devoted to tying up loose…