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NEWS

March 2024 ESRFnews

Researchers led by the CNRS

University of Rennes in France and

the University of Tokyo in Japan have

observed ultra-rapid photo-switching

of a material, using time-resolved X-ray

diffraction at the ESRF. The results

could help in the development of new

types of information storage.

Developed by the researchers

themselves, the material is from a family

of cyanide-bridged assemblies. These

compounds are multifunctional, and

can be reversibly controlled by various

changes, such as light, magnetisation

or ionic conduction. In the researchers’

material, an ultra-brief laser pulse can

prompt electron transfer between the

atoms of the crystal, switching it to

a stable state of higher volume and

altered symmetry.

Using ultra-fast crystallography at

the ESRF’s ID09 beamline, the team

showed that, beyond an excitation

threshold, the switching takes place

on an extremely fast timescale of 100

picoseconds (Nat. Commun. 15 267).

“It was a challenging experiment,

because we had to develop a powder

sample streaming technique to study

the ultra-fast dynamics towards the

permanent state, by probing a fresh

sample for each laser shot,” says Eric

Collet at the University of Rennes.

“We’ve been coming to the ESRF for

25 years now, and we’ve seen the

capabilities of the beamline and the

machine improving enormously. We

can carry out experiments today that we

couldn’t do a few years ago.”

The technique developed in the

work paves the way for the study

of various ultra-fast electronic and

structural dynamics using pump-probe

techniques, says Matteo Levantino,

the scientist in charge of ID09. “It’s

applicable to a wide range of systems,”

he says. “As the sample is a stream of

microcrystals, it is possible to obtain

high photoexcitation yields and also to

bring the system back to its initial state

by changing the sample temperature

between consecutive shots

New method to observe

ultra-fast dynamics

Researchers from the Norwegian

University of Science and Technology

(NTNU), in collaboration with

the ESRF, have used high-speed,

stroboscopic X-ray microtomography

to better understand how fluids flow

inside porous media, such as in natural

carbon-dioxide storage systems.

At high pressure and temperature,

CO

2

is in its supercritical state

between liquid and gas. In these

conditions, in porous rock

underground, it ought to be able

to displace brine, or dissolve in it,

opening up the possibility of its

storage in abandoned gas reservoirs.

But with several fluids involved,

there are many unknowns about how

buried CO

2

would behave When an

invading liquid enters a new pore for

example it can suddenly fill it rather

than flowing in a continuous manner

Named after the physicist William

Haines in 1930 this type of jump

affects the efficiency of fluid flow and

hence the storage capacity of a porous

medium but has never been observed

in 3D in detail and in real time

The NTNUESRF team have

now done this at the ESRFs ID19

beamline for water draining through

a porous medium of sintered glass

shards. Having made the drainage

dynamics repeatable, they observed

them using high-speed radiography

at different angles, and then

reconstructed individual Haines

jumps in 3D. “ID19 is unique because

it provides high flux at high X-ray

energies, and so it’s able to access

deep into the microscale structure of

natural and complex samples,” says

the NTNU’s Kim Tekseth.

The researchers found that a typical

jump can last about 20 milliseconds

– several orders of magnitude faster

than what has previously been

reported in the literature. The

results could enable the calibration

of computer models of drainage, to

predict accurately how and when

jumps will happen PNAS 121

e2305890120

The next steps for the team involve

working with different liquids

injection rates and more relevant

porous materials including real

rocks that are representative of large

scale CO

2

storage sites There are

several countries studying different

options to bury CO

2

and we want to

contribute to the feasibility of these

storage solutions saysDag Breiby at

the NTNU

ESRF coauthor

Bratislav Lukic

carries out

experiments

on ID19.

E S R F/ S T E F C A N D É

Stroboscopic X-rays show drainage

in millisecond ‘jumps’

E S R F S T E F C A N D É

We want to

contribute to

the feasibility

of CO

2

storage

solutions