From the New World of Cold Molecules
Course Number: 3237 L 381

Bretislav Friedrich

Molecular physics is undergoing a revolution whose repercussions are affecting physics at large. This revolution was precipitated by the development of techniques to cool and trap molecules. Apart from enhancing molecular spectroscopy and the ability to manipulate molecular trajectories, cold and trapped molecules are beginning to play unique roles in a number of diverse areas of fundamental interest, such as quantum collision dynamics, collective effects, and even particle physics. In this course, we’ll share in some of the excitement that has resulted from the studies of cold and trapped molecules - feats that have inspired the imagination of the entire physics community and beyond.

We’ll start by taking a detailed look at the ‘physicist’s molecule,’ a diatomic, and its interactions with electromagnetic fields (static as well as radiative) and with other molecules. We’ll also recapitulate the basic properties of lasers and of the coherent radiation they produce. Next, we’ll get acquainted with molecular beams, ubiquitous tools of modern science that enable controlled collisions between atoms, molecules and photons, keep exotic, unstable species intact, and ... wind atomic clocks. All this will make us ready to appreciate the challenges involved in cooling, slowing and trapping molecules, which we’ll take up next: we’ll introduce the techniques of buffer-gas cooling and of Stark deceleration of molecules, with their rich and appealing physics. Subsequently, we’ll consider magnetic and electrostatic trapping and storage of molecules, and discuss some of the milestone experiments in which such a fine control over molecular translation was demonstrated. As we go along, we’ll put emphasis on a good qualitative understanding of the principles involved and on the development of sound analytic models that help foster such an understanding. New, improved models may be waiting there for you to work out!

We’ll conclude our journey by taking a close look at a selection of fundamental-physics experiments conducted with cold/slow/trapped molecules in the laboratories worldwide. These will include the search for the electric dipole moment of the electron (a test of time-reversal symmetry), cold collisions at the Wigner limit, and the search for the Salam transition between optical enantiomers. At the very end, I’ll invite you to a guided tour of the cold-molecule experiments at the Fritz-Haber-Institut.



Chemistry 165. Experimental Physical Chemistry
Catalog Number: 0667

Bretislav Friedrich

Half course (spring term); Lectures: F., 1-2:30; laboratories M., or Tu., 1-5.

The course provides an introduction to the methods and techniques used in current physical chemistry research laboratories. Seven out of the total of ten laboratory assignments are experiments conducted directly in the Research Groups of the Chemistry Department. These involve: molecular beams; mass spectrometry; Fourier transform infrared and nuclear magnetic resonance spectroscopies; laser ablation; laser spectroscopy; scanning tunneling and atomic force microscopy; kinetics. Computer-based methods of data acquisition & analysis are used throughout.

Note: Recommended as an efficient preparation for research in experimental physical chemistry/chemical physics and related sciences.

Prerequisite:  Chemistry 160  or  Physics 143a.

Freshman Seminar 22t.The Unfolding Story of Light
Catalog Number: 9735      Enrollment: Limited to 12

Bretislav Friedrich

Half course (fall term). Thursdays 2-4 pm.

In the spirit of Goethe's maxim that ìA history of a science is that science itself,î the seminar will aim both to provide an understanding of light and to illuminate the historical context that made this understanding possible. Part I, Waves and photons: the development of basic concepts & ideas will first recapitulate the laws of reflection and refraction, largely known since antiquity, and discuss their impact on society and arts before Enlightenment. Next, the seminar will look at the fabric of light and review the reasons why Newton's corpuscles were washed away by Huygens' waves. The seminar will then explore Young's double-slit experiment (1801) and highlight Maxwell's interpretation of light waves as electromagnetic (1873). This will be followed by a discussion of the puzzle posed by the properties of light held at thermal equilibrium with matter, resolved in 1900 by Planck who, hesitantly, adopted the notion of a quantum of light energy. This notion, taken up in 1905 by Einstein to explain the photoelectric effect in terms of particle-like light quanta, dubbed photons, will be further examined, along with another clue to the emerging quantum science and a new understanding of light: Nernstís discovery of the vanishing heat capacity of solids at cryogenic temperatures (1910).  Einsteinís realization (1905) that the speed of light constitutes a universal ìyard stickî will also be looked at. The seminar will then consider Bohr's quantum model of the atom and of the atom's interaction with light (1913), and enjoy the crescendo of quantum ideas which ensued and culminated in the discovery of quantum mechanics and the wave-particle duality of light (1925). Relishing this story and learning key aspects of the science behind it will make the seminar ready to understand and appreciate Part II, Lasers. Laser light is coherent (which is another way of saying that it is perfect) and has innumerable applications in science & technology. The seminar will discuss some of these applications and cement its understanding of the laser through an instructive laser experiment. In Part III, Light Magic, the seminar will reflect on some of the latest science that is emerging from the laser, such as slowing and storing of light and teleportation.

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