New source for matter wave interferometry

Full text: In order to explore the transition between the quantum and the classical world we investigate the possibility of seeing non-classical interference effects with big molecules. This requires new interferometer concepts but also efficient methods to bring neutral molecules into the gas phase and to detect them selectively and efficiently after the interference. Up to now all macromolecule interference experiments were using thermal sources. But for thermo-labile particles such as for instance biomolecules even weak heating can lead to fragmentation, so that a different method is needed. We have successfully implemented a jet-cooled laser desorption source in which the molecules are first desorbed from a surface in a nanosecond laser pulse and then injected into an adiabatically expanding cooling jet of noble gas atoms. We demonstrate the efficiency of our method for the amino acids tryptophan (204 u) and the polypeptide gramicidin(1900 u) and we shed some light on the challenges and chances for proteins such as insulin (5700 u). We show that translational temperatures as low as 15 K can be reached for amino acids. Techniques for volatizing large neutral molecules will be the basis for future quantum interferometry experiments, but they will also enable further studies in the domain of slowing, cooling and spectroscopy of macromolecules. (author)