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The First-Ever Footage of a Molecule’s Spectacular Rotation

The First-Ever Footage of a Molecule’s Spectacular Rotation

An international team of scientists from four different universities was able to record the rapid spinning of a molecule using  precisely tuned pulses of laser light. “We recorded a high-resolution molecular movie of the ultrafast rotation of carbonyl sulphide as a pilot project,” said molecular physicist Evangelos Karamatskos from DESY, Germany’s largest accelerator centre.

“The level of detail we were able to achieve indicates that our method could be used to produce instructive films about the dynamics of other processes and molecules.”

651 images were constructed consecutively to span one and a half revolutions of the carbonyl sulphide molecule. The end result is a 125 picosecond film of the molecule that has been slowed down for your viewing pleasure.

“The processes we are observing here are governed by quantum mechanics. On this scale, very small objects like atoms and molecules behave differently from the everyday objects in our surroundings,” explains Küpper, who works at the University of Hamburg and DESY.

Simulated and experimental angular-distribution VMI images for selected times; the radial distributions in the simulations are extracted from the experimental distribution at 120.78 ps

“The position and momentum of a molecule cannot be determined simultaneously with the highest precision; you can only define a certain probability of finding the molecule in a specific place at a particular point in time.”

Even when the molecule points in multiple directions at the same time, each of these has a different probability according to quantum mechanics.

“It is precisely those directions and probabilities that we imaged experimentally in this study,” says molecular researcher Arnaud Rouzée from the Max Born Institute in Berlin.

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To get the gas molecules moving in sync, the researchers initially utilized two pulses of infrared laser light that were perfectly matched to each other and pulsed every 38 trillionths of a second (picosecond). Following that, a longer-wavelength laser pulse was utilized to identify the location of the molecules at intervals of roughly 0.2 trillionths of a second. Because the latter pulse kills the molecules, the entire procedure was laborious. As a result, each snapshot marks a fresh start to a new experiment.

The scientists believe that their new approach may aid in the study of other molecules and processes, such as internal twisting in molecules or chiral chemicals, which exist in two forms, one mirror image of the other.

“Furthermore, the very high degree of field-free alignment achieved here would be extremely useful for stereochemistry studies as well as for molecular-frame imaging experiments.” 

Molecular movie of ultrafast coherent rotational dynamics of OCS, Evangelos T. Karamatskos et al.

Published: July 2019

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