Innsbruck Physics Lecture - Tue, 13 Nov 2012, 17:15 lecture hall A

Wim UbachsWim Ubachs - VU University, Amsterdam

Wim Ubachs obtained his PhD degree in 1986 from the University of Nijmegen, for a thesis on high resolution laser spectroscopy. In 1986 he was a visiting scientist at the Dalian Institute of Chemical Physics (Peoples Republic of China) and in 1987-1988 he was a Post-Doctoral fellow at the Department of Chemistry at Stanford University (USA) in the group of Prof. R.N. Zare.

Since 1988 he is with VU University in Amsterdam, in the period 2000-2010 as Director of the Laser Centre VU. In the period 2001-2004 he has held a part-time Professorship at the Eindhoven University of Technology, in 2002 he was Guest Professor at ETH Zürich, and in summer 2006 at the Tokyo University of Science. Since 2003 he is full professor of Atomic, Molecular and Laser Physics at VU, mainly working in laser spectroscopy, where XUV-lasers is his specialty. For the past six years he has become deeply involved in the issue of drifting fundamental constants, and therewith in astronomical observations. He has co-authored over 200 scientific papers (see ).

Search for a variation of fundamental constants

Since the days of Dirac scientists have speculated about the possibility that the laws of nature, and the fundamental constants appearing in those laws, are not rock-solid and eternal but may be subject to change in time or space. Such a scenario of evolving constants might provide an answer to the deepest puzzle of contemporary science, namely why the conditions in our local Universe allow for extreme complexity: the fine-tuning problem. In the past decade it has been established that spectral lines of atoms and molecules, which can currently be measured at ever-higher accuracies, form an ideal test ground for probing drifting constants. This has brought this subject from the realm of metaphysics to that of experimental science. In particular the spectra of molecules are sensitive for probing a variation of the proton-electron mass ratio m, either on a cosmological time scale, or on a laboratory time scale. A comparison can be made between spectra of molecular hydrogen observed in the laboratory and at a high redshift (z=2-3), using the Very Large Telescope (Paranal, Chile) and the Keck telescope (Hawaii). This puts a constraint on a varying mass ratio Δμ/μ at the 10-5 level. The optical work can also be extended to include CO molecules. Further a novel direction will be discussed: it was discovered that molecules exhibiting hindered internal rotation have spectral lines in the radio-spectrum that are extremely sensitive to a varying proton-electron mass ratio. Such lines in the spectrum of methanol were recently observed with the radio-telescope in Effelsberg (Germany).

For a picture of the Effelsberg radiotelescope in operation see:

Video recording of the lecture

Loading the player...

Previous lectures

Michael Kramer - Nearly 100 years after General Relativity: Was Einstein right? >>
(04 November 2014)

Immanuel Bloch - Controlling and Exploring Quantum Matter at the Single Atom Level >>
(22 October 2013)

Wim Ubachs - Search for a variation of fundamental constants >>
(13 November 2012)

Reinhard Genzel - Massive Black Holes and Galaxies >>
(4 October 2011)