Wave nature of Biomolecules and Fluorofullerenes

Lucia Hackermüller, Stefan Uttenthaler, Klaus Hornberger,
Elisabeth Reiger, Björn Brezger, Anton Zeilinger and Markus Arndt


Since Louis de Broglie's hypothesis that all massive particles should also show wave behavior many exciting experiments have studied interference of electrons, neutrons, atoms and molecules. Up to now the mass and complexity record was held by the highly symmetric fullerene molecules C60 and C70
( more details).  

Our goal is to further explore the limits of quantum mechanics with even larger objects which consist of many strongly bound atoms,  investigated at  high temperatures.


Here we demonstrate for the first time the quantum wave nature of  a small biomolecule, the  porphyrin (top right) and the fluorinated fullerenes C60F48 which is the heaviest molecule up to now (1632 amu) to show its wave nature (left)

What happens in the experiment ...

Porphyrins and fluorinated fullerenes are vaporized in a thermal source (an oven). On their way to the detector
they pass a near field interferometer in a vacuum chamber, at a pressure of 10-8 mbar which is sufficient to prevent the molecular wave from decoherence. ( more details on the pressure dependence)
 The interferometer consists of three equally spaced gratings, the first one prepares the required coherence, the second one leads to the formation of a diffraction image in the plane of the third grating, which is used as a mask, which determines the spatial resolution of the molecule detector. After passing the third grating the molecules are ionized by use of an electron beam, mass selected and detected in a quadrupole mass spectrometer.

Sketch of Talbot-Lau inerferometer

Fig.3 Schematic setup of the near-field interferometer for porphyrins & fluorinated fullerenes. 

The Nearfield Interferometer.

Interference fringes of porphyrins

Porphyrins (the exact name would be: meso-tetraphenylporphyrin C44H30N4) are very 'classical' objects  in the sense that they are abundant and relevant in living nature: they are part of the color centers in chlorophyll or heme, and they are used at high temperatures. The shape of porphyrins differs significantly from the previously used round fullerenes:  they are twice as extended, and have an aspect ratio (height to width) of about 7:1.
While one could have speculated that this asymmetry might make the molecules more prone to couplings with their environemnt which could ultimately destroy the interference,  our experiment proves the contrary in that it shows quantum interference fringes with the expected fringe visibility.

Interference fringes of Porphyrin

Fig.4 Interference fringes of porphyrin 

Interference fringes of fluorinated fullerenes

We have also observed quantum interference with fluorinated fullerenes, which are deformed buckyballs with a shell of 48 fluorine atoms. Allthough the experiments were much more demanding with this object (due to count rate and background limitations) we have observed a fringe visibility that gives us very good evidence for the quantum wave behaviour of this object.

C60F48 holds currently the new record in complexity (108 atoms), mass (1632 amu) for matter wave interferometry.

Interference fringes of C60F48

Fig. 5
The interferogram of C60F48   




Links to other experiments by our group


Lucia Hackermüller, Klaus Hornberger  & Markus Arndt 09/2003