Observing a molecule stretch and bend in real-time

An international study, led by ICFO, has observed the bending and stretching of a triatomic molecule with combined attosecond and picometre resolution.

Illustration of the ultrafast stretching and bending of a linear triatomic molecule and subsequent direct imaging with laser-induced electron diffraction. Image Credit: ICFO/K. Amini and U. Jena
Illustration of the ultrafast stretching and bending of a linear triatomic molecule and subsequent direct imaging with laser-induced electron diffraction. Image Credit: ICFO/K. Amini and U. Jena

Seeing how particles bend, stretch, break or change amid concoction response requires an extent, cutting edge instruments and procedures that can observe and track, with sub-atomic spatial and few femtoseconds fleeting goals, each atom inside a molecule and how they carry on amid such a change.

Almost before 2 decades, scientists had developed a method that uses molecules’ own electron to capture its snapshots of the structure in real time. Next approach that comes in 2016, was able to achieve the required spatial and temporal resolution to take snapshots of molecular dynamics without missing any of its events, reporting on the imaging of molecular bond breakup in acetylene (C2H2) [Science 354, 308 (2016)].

Now, a team of scientists at ICFO have observed the structural bending and stretching of the triatomic molecular compound carbon disulphide, CS2 by using a modern approach. They have gone beyond their previous discovery and achieved another amazing milestone in their research.

Scientists observed the phenomenon using laser-induced electron diffraction, a molecular-scale electron microscope that allows scientists to peer into the molecular world to capture clean snapshots of the molecule’s geometry with combined sub-atomic picometre (pm; 1 pm = 10-12 m) and attosecond (as; 1 as = 10-18 s) spatio-temporal resolution.

They reported that the ultrafast modifications in the molecular structure are driven by changes in the electronic structure of the molecule, governed by an effect known as the Renner-Teller effect. Such effect is key for important triatomic molecules such as carbon disulphide, CS2, since it can determine specific chemical reactions in our earth’s atmosphere that could, for example, affect the climate conditions.

This is for the first time, scientists successfully imaged this effect during their experiment. They obtained snapshots in real time, seeing the molecule stretch symmetrically and bend in a linear-to-bent structural transition within ~85 fs (8 laser cycles).

They made it possible by using a state-of-the-art quantum microscope composed of: (i) a mid-infrared 3.1 micrometer intense, femtosecond laser system that illuminates a single CS2 molecule with 160,000 laser pulses per second; and (ii) a reaction microscope spectrometer that can simultaneously detect the full three-dimensional momentum distribution of the electron and ion particles generated from the ionization and sub-cycle recollision imaging of a single isolated molecule.

To affirm their trial discoveries, the group likewise performed state-of-the-art quantum dynamical theoretical simulations, and verified the match between theoretical and observational results, confirming that ultrafast linear-to-bent transition is indeed enabled by the Renner-Teller effect. Such discoveries connote a noteworthy advance forward in understanding the basic impacts that occur in atomic unique systems.

The study published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). Co-authors include ICFO researchers Dr. Kasra Amini, Dr. Michele Sclafani, Dr. Tobias Steinle, Aurelien Sanchez, led by ICREA Prof. at ICFO Dr. Jens Biegert.

This study was carried out together with ICREA Professors at ICFO Maciej Lewenstein and Javier García de Abajo and former ICFO researchers Jose Martinez, Michael Hemmer, Michael Pullen, and Benjamin Wolter, in collaboration with researchers from University of Warsaw, Kansas State University, Friedrich-Schiller University Jena and the Abbe Center of Photonics, the Max-Planck-Institute für Kernphysik in Heidelberg, and Physikalisch-Technische Bundesanstalt in Braunschweig.