2013 December

Time-resolved Imaging of Cold Molecules on a Molecule Chip

Wednesday, 18th December 2013Publication highlights

Molecule Chip with Integrated Detection. Molecules are ionized in the detection region of the chip, then imaged using ion optics to create a spatial image of the molecular ensemble.

In the quest for ever more control over molecules, researchers at the Fritz Haber Institute of the Max Planck Society have now added the final fundamental component to the molecule chip, namely the ability to detect molecules on the chip. In fact, they were able to go even further and produce time-resolved images of the molecules.

The molecule chip is the molecule analog of the atom chip and ion chip.  Whilst atom chips and ion chips are extremely well developed for the control of many and single particle systems, the molecule chip is in its infancy.

The molecule chips developed thus far are arrays of microelectrodes deposited on a substrate (either glass or silicon).  Whilst they have been shown to be able to trap and manipulate the external and internal degrees of freedom of cold gas-phase molecules, detection to date has had to be carried out using external detectors situated tens of centimetres away from the chip. For the goal of investigating short-lived quantum states or resolving the spatial dynamics of molecular interactions, the long times required to reach external detectors are far from suitable.

In their new work highlighted in Physical Review Letters, Silvio Marx and his colleagues have built a new molecule chip that incorporates a specially designed detection region in which the molecules are ionized. The ions are then guided away from the chip using ion optics integrated onto the chip and then spatially imaged onto a detector using a set of ion lenses. In this way, an image of the original spatial distribution of the molecules is created. Moreover, time-resolved images can be taken, mapping the evolution of the system in time-of-flight. This gives the researchers valuable information about the phase-space distribution of the molecules, from which one can extract, for example, the temperature of the molecular ensemble.

The realisation of a fully integrated molecule chip now offers the ability of trapping, manipulation and detection – a new and promising route for the investigation of cold trapped samples of molecules.

Imaging Cold Molecules on a Chip
S. Marx, D. Adu Smith, M. J. Abel, T. Zehentbauer, G. Meijer, and G. Santambrogio
Phys. Rev. Lett. 111, 243007 (2013)

Link to Paper: http://prl.aps.org/abstract/PRL/v111/i24/e243007
Link to Highlighted Paper Synopsis: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.111.243007

Every atom counts

Monday, 2nd December 2013Publication highlights

Although the local environment of a molecule can play an important role in its chemistry, rarely has it been examined experimentally at the level of individual molecules. Here we report the precise control of intramolecular hydrogen-transfer (tautomerization) reactions in single molecules using scanning tunnelling microscopy. By placing, with atomic precision, a copper adatom close to a porphycene molecule, we found that the tautomerization rates could be tuned up and down in a controlled fashion, surprisingly also at rather large separations. Furthermore, we extended our study to molecular assemblies in which even the arrangement of the pyrrolic hydrogen atoms in the neighbouring molecule influences the tautomerization reaction in a given porphycene, with positive and negative cooperativity effects. Our results highlight the importance of controlling the environment of molecules with atomic precision and demonstrate the potential to regulate processes that occur in a single molecule.

Online publication in Nature Chemistry on Dezember 1, 2013,
Controlling intramolecular hydrogen transfer in a porphycene molecule with single atoms or molecules located nearby
Takashi Kumagai et al.

Nature Chemistry, doi: 10.1038/nchem.1804

For more information please contact:

Prof. Dr. Leonhard Grill, Fritz-Haber-Institut der Max-Planck-Gesellschaft,

Tel.:  ++43 316 380 5412, E-Mail: lgr@fhi-berlin.mpg.de