On March 23, 2024, Science Synergy Science Chair Dr. Noah Bray-Ali will speak at the Spring 2024 Meeting of the Southern California chapter of the American Association of Physics Teachers on the campus of Loyola Marymount University. The talk has to do with quartz crystal which is the most common mineral in the crust of the Earth. The laser Raman light scattering spectrum of quartz crystal has a broad peak in the intensity of scattered light at a frequency shift that corresponds to the rest-mass of the particles–known as axions–that form the dark matter in the universe.
During Raman light scattering, the incoming and outgoing visible light interfere within the quartz crystal. The shift in the frequency of the scattered light compared to the incoming light means that the interference creates an electromagnetic wave that oscillates with frequency equal to this shift. This wave at the “beat note” combines with the static electricity within the quartz crystal to make axions–the particles that form the dark matter–provided that the frequency shift lands on the rest-mass energy of the axion.
The rest-mass energy of the axion follows from the combination of three pieces of information: (1) The energy in the form of dark matter in the Universe, (2) the number of dark matter particles, and (3) the fact that dark matter is now cold and is made of axions (See Making Dark Matter in the Big Bang). Dividing the energy by the number gives the energy per particle. The result is simply the rest-mass energy of the axion for cold dark matter that is made of axions.