Modern Physics Experiments
Physics 3340/4430/5430 Spring Semester, 2006
For each of these experiments there is a write-up that provides a description of the equipment and the physical phenomena involved. It also gives a set of measurement goals, but usually not a detailed procedure. You must develop your own procedure for best achieving these goals. All of these experiments are somewhat open‑ended in that they offer opportunities for you to pursue additional research topics, and you are encouraged to investigate additional topics of your own choosing. All the experiments typically take 3 weeks to complete if you do the basic minimum experiment. This assumes you put in something like 6 hours per week in the lab and prepare ahead of time. If you pursue additional topics (with the permission of the instructor) they can take much longer.)
1. Absolute Measurement of the Faraday. Measurement of the Faraday in terms of SI units of mass, length, and time. (The Faraday is the charge in Coulombs of Avogadro's number of electrons.)
2. Scanning tunneling microscope. The STM is used to study a variety of surfaces with atomic resolution. After first exploring the basic tunneling phenomena, students observe gold, graphite, and other surfaces and measure the atomic structures of the surfaces.
3.
Gamma
ray spectroscopy. This experiment uses a NaI
crystal and the photoelectric effect to obtain spectra of the gamma rays
emitted by various sources.
4. Pulsed nuclear magnetic resonance. The dynamic behavior of nuclear spins is investigated using pulsed magnetic resonance techniques. Spin echoes and spin relaxation rates are studied in various samples. NOTE—the writeup for this experiment is not yet available on-line.
5. Laser spectroscopy. Narrowband tunable diode lasers are used to carry out high-resolution spectroscopy of atomic rubidium. The technique of saturated absorption spectroscopy will be studied to obtain resolution greater than the Doppler width of the resonance lines. The excited state hyperfine structure will be measured.
6. Laser trapping and cooling. Light from tunable diode lasers is used to cool and trap rubidium atoms. The forces exerted by the laser light are used to hold atoms at a point in space and cool them to less than 1 mK above absolute zero. The laser spectroscopy experiment is a prerequisite for doing this experiment, and some of the same apparatus is used in both. This is best done as a “capstone” experiment; i.e. as the last lab.
7. Lifetime of muons generated by cosmic rays. This experiment uses large plastic scintillators with attached photomultiplier tubes. Cosmic rays are studied by observing the light pulses they produce in the scintillators. A variety of fast timing electronics and coincidence circuits are used to obtain information about the composition and characteristics of the cosmic rays, but the specific measurements and studies are designed by the student. Muon lifetime measurement is a good first effort.
8. Soliton propagation. This experiment uses an electronic circuit board to illustrate the propagation of electromagnetic solitons.