Quantum Mechanics Part 2

fn1_1h_qm2_cr.pptOne of the things you might be wondering is how do you teach someone quantum physics when they only have had high school algebra and why do you teach someone quantum physics in Nanoscience. To answer the first question I would say that you don't have to do all of the differential equations to teach someone about quantum physics. Mostly I want to emphasize the concepts.The reason I want to introduce quantum physics at this point is because it underlies the operating principles of many of the tools and devices used in nanoscience.The next topic is descretization of energy and characteristic energy. Having the background of working with standing waves and introducing nodes to standing waves should give the students a better chance of understanding how energy is quantized when you are dealing with standing waves. The change when you go from a 1s -> 2s -> 3s orbital is the introduction of spherical nodes. As you go from 2p->3p->4p you introduce a spherical node each time you increase in energy. The idea of nodes can be seen in a spring like a Slinky or in a flute or whistle when you blow harder to generate octaves. A good transition on the way to 3 dimensional standing waves is to consider a drum head that is vibrating which can be viewed at the following web site:http://www.kettering.edu/~drussell/Demos/MembraneCircle/Circle.htmla href="http://hyperphysics.phy-astr.gsu.edu/Hbase/music/cirmem.html">http://hyperphysics.phy-astr.gsu.edu/Hbase/music/cirmem.htmlI wish I had a demonstration of this. Maybe I could put some particles on a drum head and get it vibrating to show the different nodes.I just came across this video which indicates waves and nodes in the Tacoma Bridge collapse:https://www.youtube.com/watch?v=3mclp9QmCGsGiven that the energy levels of electrons in atoms is quantized I then continue on to show that different elements have different characteristic spectra. Based on these spectra we can identify the elements/atoms present in a sample. I use diffraction grating glasses obtained from Rainbow Symphony:http://www.rainbowsymphonystore.com/difgratglas.htmlWe get these with our logo printed on them to give away as a promotional item. I use these with a gas tube light. You can get these from Science Kit with different gasses in them. I usually show Helium in this demonstration because it has very nice lines but I also like to have Argon and Nitrogen available so you know what to look for in a plasma reactor to tell if it has a leak. Nitrogen, of course, is quite pink so that is a good indication of a leaky reactor if you see a pink color.For infra-red spectroscopy I have the students put their hands out on either side of their had in a Y shape and then we demonstrate the bending, vibration and rotation of molecular bonds that occur at infrared frequencies.I want to introduce them to quantum numbers early on because they will continue to have trouble with it throughout the course. I use quantum numbers later to determine allowed X-ray transitions when we teach EDS and other X-ray analyses.This is a good time to bring up electron spin which we will use later in spintronic devices.The next topic is the tunneling effect. I demonstrate this with the following web site:http://www.quantum-physics.polytechnique.fr/index.htmlThere are a lot of good quantum physics simulations here but the one I am most interested in is 1.5 Wave Mechanics: Steps and Barriers, and inparticular how the amount of tunneling increases exponentially as the thickness of the barrier decreases. This will become the basis for the scanning tunneling microscope operation which we cover later.What are the applications of quantum mechanics?1. Photoelectric effect: This forms the basis for the photovoltaic cell. This is also important in the function of the electron microscope.2. Characteristic energy: This forms the basis of spectroscopy: UV-Vis, FTIR, X-Ray, Raman3. Wave particle duality: The electron microscope is able to image with electrons. The ultimate resolution of the electron microscope comes from the wavelength of the electron.4. Electron spin: Not just for the Pauli exclusion principle anymore, electron spin gives rise to spintronics, computer hard disk drives and MRAM technology using spin valves and magnetic tunnel junction.5. Electron tunneling: This effect is used in the scanning tunneling microscope, the field emission electron microscope as well as the magnetic tunnel junction MRAM devices and becomes a consideration when gate oxides become very thin.6. Quantum numbers: Forms the basis for quantum computing and quantum entanglement.I do a brief discussion here on quantum computers and why they are important. The development of a powerful quantum computer would invalidate all current encryption methods and make all current forms of electronic financial transactions obsolete. On the other had quantum encryption could result in an "unbreakable" encryption scheme. I mention the qubit which has states 1, 0 and indeterminate. Some students become very interested in quantum computing and like to do reports on it.Finally we will move on to the next unit which is Nanoscience tools and we start with the optical microscope.

Quantum Mechanics Part 2

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