Max-Planck-Institute of Quantum Optics &
Faculty of Physics, Ludwig-Maximilians-Universität
Thursday, March 1st 2012, 18:00
Stephen Leacock Building, Leacock Auditorium (room 132)
Passion for Precision
The Balmer spectrum of atomic hydrogen has provided the Rosetta stone
for deciphering the strange laws of quantum physics during the early 20th
century. Precise spectroscopy of the simple hydrogen atom can yield accurate
values of important physical constants and it can stringently test basic
physics laws. The invention of the laser frequency comb a decade ago has
given us a tool for accurately counting the ripples of a light wave, so that
we are now able to measure resonance frequencies in hydrogen to 15 decimal
digits. Recently, it has become possible to perform laser spectroscopy of
exotic muonic hydrogen, where the electron is replaced by 200 times heavier
muon. The measured 2S - 2P Lamb shift gives an accurate value of the charge
radius of the proton. However, this radius is significantly smaller than
the value obtained from spectroscopy of ordinary hydrogen or from electron
scattering experiments. This proton size puzzle is subject of intense
discussions. It may be caused by a mistake, or it may indicate a dent in
the armor of quantum electrodynamic theory.
Friday, March 2nd 2012, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112)
What can we do with laser frequency combs?
The spectrum of a mode-locked femtosecond laser consists of several hundred
thousand precisely evenly spaced spectral lines. Such laser frequency combs
have revolutionized the art measuring the frequency of light, and they
provide the long-missing clockwork for optical atomic clocks. High harmonic
generation with intense femtosecond pulses provides a path to extend frequency
comb techniques into the extreme ultraviolet and perhaps into the soft x-ray
regime. Laser comb techniques can give control of the electric field of
ultrashort laser pulses, and they have become key tools for the emerging
field of attosecond science. The availability of commercial instruments
is facilitating the evolution of new applications far beyond the original
purpose, ranging from from fundamental research to telecommunications and
satellite navigation. Laser combs are revolutionizing molecular spectroscopy
by dramatically extending the resolution and recording speed of Fourier
spectrometers.The calibration of astronomical spectrographs with laser combs
will enable new searches for earth-like planets in distant solar systems,
and may reveal the continuing expansion of space in the universe.
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