Scientists are now one step closer to better understanding how to live in a
"quantum" world—and not just from watching the character "Ant-Man" in the
Marvel movie franchise.
Take, for instance, a microscopic view of the delicate, protective barrier
of the Earth's atmosphere that creates the ozone layer and protects life as
we know it. Inside that layer of air, oxygen molecules are under near
constant attack by solar ultraviolet (UV) rays that break up these molecules
through a chemical process known as photodissociation. While this process is
invisible to the naked eye, scientists can observe these micro-interactions
on the smallest of scales—the quantum level.
In a study recently published in Science, scientists at the University of
Missouri provide evidence of the effects of photodissociation on the quantum
level for an atmospheric pollutant, formaldehyde, thereby showing
photodissociation reactions can't be treated classically, like billiard
balls coming together, colliding and reconnecting, said Arthur Suits,
Curators Distinguished Professor of Chemistry in the MU College of Arts and
Science, and a co-corresponding author on the study.
"By only thinking of chemical reactions in the classic sense with 'billiard
balls,' a chemist is going to miss out on what a molecule is truly doing,"
Suits said. "It is well known that quantum effects are very important as a
molecule gets very cold. What is surprising here is that strong quantum
effects appear at the high energy of photodissociation. This new insight
could change not only our view of how the molecule behaves, but may also
impact the overall chemical makeup, and that in turn could cause the
chemistry to go in unexpected ways because of this added dimension of the
quantum properties."
The new study concerns roaming, in which photodissociation breaks a molecule
into pieces, but the pieces come back and react with each other. Until now,
"billiard ball" models could completely match such experiments. The study
shows more detailed measurements cannot be treated this way.
Instead, they have to use a more complicated quantum model to confirm the
unusual properties they are observing. Suits believes their findings could
one day help scientists develop a better theoretical understanding of the
chemistry in the atmosphere, both in the stratosphere where ozone protects
us, and at ground level where it is a dangerous pollutant.
"If you want to understand the chemistry of the atmosphere, for example, you
first need to understand what happens when light is absorbed and a molecule
starts to dissociate," Suits said. "Chemists may think they don't have to
worry about what is going on at the quantum level in photodissociation, and
it's just the classic billiard-ball effect of atoms, but we show here that's
not always the case, and chemists need to be able to refine their intuition
to a certain extent."
"Orbiting resonances in formaldehyde reveal coupling of roaming, radical,
and molecular channels," was published in Science. Co-authors include Casey
Foley at MU, and Hua Guo and Changjian Xie from the University of New
Mexico. Xie also has a dual appointment with Northwest University in China.
Reference:
Casey D. Foley et al, Orbiting resonances in formaldehyde reveal coupling of
roaming, radical, and molecular channels, Science (2021).
DOI: 10.1126/science.abk0634
Tags:
Physics