Hamburg 2009 – scientific programme

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SYHR: High resolution spectroscopy – modern trends and new techniques

SYHR 2: High resolution spectroscopy - modern trends and new techniques II

SYHR 2.1: Invited Talk

Thursday, March 5, 2009, 14:00–14:40, VMP 8 R05

Microwave Spectroscopy of Weakly Bound Systems and Floppy Molecules — •Wolfgang Stahl — Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany

FT microwave spectroscopy using molecular beams is an excellent tool to study weakly bound systems like rare gas clusters and hydrogen bonded systems. Here the molecular beam conditions are necessary to form these species and the inherently high resolution of FT microwave spectroscopy allows to accurately determine their structure and dynamics. However, experimental and also theoretical limitations exist. Experimentally, the rather low sensitivity of FT microwave spectroscopy compared to other methods is probably a bigger problem than resolution. The biggest theoretical limitation is currently the proper treatment of large amplitude motions which are almost always present in weakly bound systems but also in stable molecules. Here in recent years some progress has been made, however, due to the multidimensional potentials found in many weakly bound systems assignment of the spectra is difficult and sometimes impossible. In many cases only fundamental states have been analyzed but also many observed transitions remain unassigned. Including these lines which often are due to higher tunneling states would provide a source for parameters describing the potential surface.

Some examples for solved and yet unsolved problems with weakly bound systems and floppy molecules will be discussed.