Physicists take stop-action images of light-driven molecular reaction


Date:
July 20, 2020
Source:
Kansas State University
Summary:
Physicists have taken extremely fast snapshots of light-induced
molecular ring-opening reactions -- similar to those that help a
human body produce vitamin D from sunlight.



FULL STORY ========================================================================== Kansas State University physicists have taken extremely fast snapshots
of light-induced molecular ring-opening reactions -- similar to those
that help a human body produce vitamin D from sunlight. The research is published in Nature Chemistry.


========================================================================== "Think of this as stop-motion like a cartoon," said Daniel
Rolles, associate professor of physics and the study's principal
investigator. "For each molecule, you start the reaction with a laser
pulse, take snapshots of what it looks like as time passes and then
put them together. This creates a 'molecular movie' that shows how the electronic structure of the molecule changes as a function of how much
time passes between when we start and when we stop." Shashank Pathak,
doctoral student and lead author on the paper, said the idea was to
study the dynamics of how a ring opens in a molecule on the time scale
of femtosecond, which is one quadrillionth of a second. The researchers
use a free-electron laser to visualize how these reactions happen by
recording electron energy spectra as the atoms in the molecule move apart.

"The ring opening reaction is observed in nature quite a bit," Pathak
said.

"One example is the formation of vitamin D3 in our skin. When sunlight
shines on our skin, we have big compounds that have these small ring
structures that help with the absorption of UV light. The ring opens to
form the precursor to vitamin D3 formation." Making vitamin D involves
various biological functions and this ring opening is just one small --
very small -- part of the process, Pathak said. This research was able
to record the changes in the molecule in order to understand the speed
of the process, how it happens and compare the process to previously
accepted theory.

"Understanding the process has implications for making similar processes
that can be used in technology more efficient, and for developing
general rules that can be applied to similar reactions," said Rolles,
who received a National Science Foundation Faculty Early CAREER award
in 2018 that funded this research.


========================================================================== Story Source: Materials provided by Kansas_State_University. Original
written by Stephanie Jacques. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Shashank Pathak, Lea M. Ibele, Rebecca Boll, Carlo Callegari,
Alexander
Demidovich, Benjamin Erk, Raimund Feifel, Ruaridh Forbes, Michele Di
Fraia, Luca Giannessi, Christopher S. Hansen, David M. P. Holland,
Rebecca A. Ingle, Robert Mason, Oksana Plekan, Kevin C. Prince,
Arnaud Rouze'e, Richard J. Squibb, Jan Tross, Michael N. R. Ashfold,
Basile F.

E. Curchod, Daniel Rolles. Tracking the ultraviolet-induced
photochemistry of thiophenone during and after ultrafast ring
opening.

Nature Chemistry, 2020; DOI: 10.1038/s41557-020-0507-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200720132553.htm

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