Experiments during Wintersemester 2021
E-Mail: sgraham (at) pi5.physik.uni-stuttgart.de
Room: 1.570 Tel.: 64849
A better understanding of material properties allows us to manipulate them and create new compounds with better electronic, mechanic and optical properties. However such an understanding requires the knowledge of the detailed structure of the materials, because without this knowledge one is as lost as in unknown territory without a map. With X-ray diffraction structural parameters of crystalline materials can be determined with high precision. In this experiment the basic principles of X-ray diffraction are developed. For this purpose in the first part of the experiment the properties of X-rays and their absorption characteristics are investigated with an X-ray apparatus. In the second part the structural properties and parameters of single crystals are determined with X-ray diffraction.
Generation and absorption of X-rays, crystalline structure, lattice, reciprocal lattice, Bragg reflection, Laue equations, X-ray tubes, counter tube, Compton effect, x-ray fluorescence.
E-Mail: ananya.biswas (at) pi1.uni-stuttgart.de
Room: 1.943 Tel.:
When light hits matter it gets scattered. Mostly this happens in form of elastics scattering (Rayleigh scattering), where the molecule almost instantly reemits the entire absorbed photon energy with the same frequency. However the excited molecule can absorb (or emit) a (small) part of the photon energy e.g. as molecular vibrations and emit light with a smaller (or larger) frequency. This is called Raman-scattering. The Raman spectrum is characteristic for each molecule and each crystal. From the energy difference to the incident light and the polarization degree of the scattered light and with the help of group theory one can gain informtation on the atomic structure of the samples. The selection rules for Raman- and IR spectroscopy differ in a way that both methods complement each other very well. In the experiment the Raman spectra of CHCl3, CHBr3, CdCl3 und CdBr3 are measured. In the setup the light from a HeNe-Laser scattered off the sample is analyzed with a spectrometer. For the evaluation the measured Raman spectra are compared for these molecules with group theory and assigned to their corresponding group. The Boltzmannn contstant is determined from the intensity ratio between Stokes- and Antistokes lines. Keywords: Raman transitions (Stokes and Antistokes), vibrational spectroscopy, group theory of simple symmetries
E-Mail: kng (at) pi5.physik.uni-stuttgart.de
Room: 1.543 Tel.: 64867
In this students’ lab a simple He-Ne-Laser is aligned for different output mirrors.The stability ranges for different resonator arrangements and the laser gain are determined. Also the axial development of the laser beam is visualized by a CCD camera and will be measured. By different frequency selective optical elements inside the resonator the laser is operated at different wavelength. The output wavelength is thereby determined by a CCD spectrometer. The axial modes of a He-Ne-Laser will be examined with a Fabry-Pérot-Interferometer. Key words Laser conditions, laser types, 2-,3-,4- level laser, stimulated and spontaneous emission, absorption, line broadening mechanism, laser modes, free spectral range, finesse, axial and transversal modes, Fabry-Pérot-Interferometer.
E-Mail: anasuri (at) pi5.physik.uni-stuttgart.de
Room: 1.939 Tel.: 64864
In a measurement, the demanded information is often given in a time-dependent voltage signal, in the so called time domain. With an oscilloscope, you can record these signals. However, the desired information is often coded in frequency, so one is only interested in particular frequencies. With the aid of a spectrum analyser, the desired signals can be visualized in the frequency domain. Using examples of simple physical experiments (acoustic resonator, coupled oscillator, fluxgate magnetometer), the experiment demonstrates the versatile possibilities of Fourier methods. Where the oscilloscope just detects noise, you can detect signals in the Fourier space, which differ in amplitude by a factor of 10.000. Aside, a spectrum analyser is excellently qualified for analysing amplitude- or frequency-modulated signals or for the characterisation of nonlinearities.