- Date: Nov 3, 2015
- Time: 14:30 - 16:00
- Speaker: Prof. Dr. Wim Ubachs, Department of Physics and Astronomy, VU University, Amsterdam, Netherlands
- Room: Herbert Walther Lecture Hall
- Host: MPQ

The spectrum of molecular hydrogen H2 can be measured in the laboratory to very high precision using advanced laser and molecular beam techniques, as well as frequency-comb based calibration.

The quantum level structure of this smallest neutral molecule can now be
calculated to very high precision, based on a very accurate Born-
Oppenheimer potential and including subtle non-adiabatic, relativistic
and quantum electrodynamic effects. Comparison between theory and
experiment yields a test of QED, and in fact of the Standard Model of
Physics, since the weak, strong and gravitational forces have a
negligible effect. Even fifth forces beyond the Standard Model can be
searched for. Astronomical observation of molecular hydrogen spectra,
using the largest telescopes on Earth and in space, may reveal possible
variations of fundamental constants on a cosmological time scale. A
study has been performed at a look-back time of 12.5 billion years. In
addition the possible dependence of a fundamental constant on a
gravitational field has been investigated from observation of molecular
hydrogen in the photospheres of white dwarfs. The latter involves a test
of the Einstein’s equivalence principle.

http://www.mpq.mpg.de/events/7238/5381684