The advanced physics practical course (FP) is a compulsory course in the bachelor's degree program in physics. It focuses on experiments from all areas of physics supervised in the research groups of the Institute of Solid State Physics, Institute of Optics and Atomic Physics and Berlin research institutes. The practical course is organized by Dr. Tim Wernicke from the Solid State Physics group. Details can be found on the homepage of the advanced physics practical course.
This modern project experiment P07 was set up stepwise in the period 2007-2010 in the Dopfer group. It offers basic knowledge in many different areas of experimental physics (molecular spectroscopy, optics, laser, resonators, vacuum, atmospheric and environmental physics). The technique of Cavity-Enhanced Absorption Spectroscopy (CEAS) is, along the with the related method of Cavity-Ringdown Spectroscopy (CRDS), the most sensitive approach for sensing trace gases. It relies on resonator-enhanced absorption in a cavity of highly reflective mirrors (R>0.9994), reaching effective absorption lengths of several km. In this experiment, CEAS is employed to measure the multiple forbidden electronic transition of molecular oxygen (O2) at very high spectral resolution. To this end, we determine fundamental molecular constants of O2 such as rotational constants and collision cross sections. Hence, this experiment provides deep insight into molecular physics using the example of O2, the second most abundant molecule in our atmosphere. The measured transition does not only play an important role for the radiation balance of the earth atmosphere but may also be used to detect O2 (and thus life as we know it) in the atmosphere of exoplanets with telescopes (astrobiology).
Spectroscopy & Molecular Physics
Atmospheric & Climate Physics
Analysis & Protocol
Info about this experiment can be found on the Study & Teaching web pages of AG Wolters.
As part of the 2018 Long Night of Science, a working replica of the first beamline for two-stage imaging with electrons was developed based on Ernst Ruska's model to repeat his groundbreaking 1931 experiment . The replica is now a permanent part of the advanced practical course and provides physics students with a unique approach to electron optics, as a dedicated transmission electron microscope (TEM) is built for imaging and diffraction as part of the FP experiment.
 M. Knoll and E. Ruska, Ann. Physik 12, 607 and 641 (1932)
Learning objectives and methods:
The experiment is supervised by Frederik Otto from AG Lehmann.
The question "How can a particle interfere with itself?" is always a hot topic among physicists. In this experiment you will not find out the answer, because there is none within the scope of our (limited) horizon of experience; nevertheless, you will experience that electrons sometimes behave as particles, sometimes as waves. Thereby the concept of coherence takes a wide space. In addition, the experiment will introduce you to the basics of off-axis electron holography and give you a taste of the usefulness of the Fourier transform. The experiment will take place on the FEI Titan 80-300 Berlin Holography Special electron microscope, which is one of the best electron microscopes in the world for electron holography.
Learning objectives and methods:
The experiment is supervised by Dr. Tore Niermann from AG Lehmann.