laser heating – Lightsources.org

Matter under extreme conditions, especially at extreme temperatures and pressures, plays an important role in many fields. These range from astrophysics and geology over inertial fusion reactor studies to applied research on material processing by laser ablation. Due to the complex behaviour of matter under such conditions the underlying interactions are not yet fully understood. In recent years isolated nanoparticles, which form well-defined crystalline structures at lower temperatures, have proven to be suitable test objects for the study of such questions.

A team of researchers including DESY scientists around Daniela Rupp (ETH Zurich), Thomas Möller (TU Berlin) and Bernd v. Issendorff (Univ. Freiburg), as well as several groups from Univ. Rostock (Ingo Barke, Karl-Heinz Meiwes-Broer, Thomas Fennel), has applied time-resolved soft X-ray diffraction at the CAMP endstation at FLASH to study the dynamics of superheated silver nanoparticles in a laser pump – FEL probe experiment. They observed that silver nanoparticles, when strongly laser-heated via their plasmon resonance, exhibit a wide range of phenomena, from melting over cavitation-induced bubble-like expansion to explosion, as a function of the excitation strength. “Depending on the heating conditions and the temporal evolution, we could identify different classes of diffraction images, stemming from faceted, round, hollow, fragmenting or sometimes finally exploding nanoparticles”, Alessandro Colombo (ETH Zurich), one of the three first authors, explains.

Read more on DESY website

Image: Diffraction image of a hollow silver nanoparticle (left) measured at FLASH, along with its reconstruction (top right) and a corresponding picture from MD simulations (bottom right).

Credit: T. Reichenbach, Univ. Freiburg

A team led by the University of Bayreuth (Germany) has synthesized, for the first time, new materials at terapascal pressures, using the ESRF’s ID11 and a unique diamond anvil cell. The results are published in the journal Nature.

Matter changes with variations of pressure and temperature, which allows the tuning of many material properties. These possibilities can shed light onto scientific questions, such as the fundamental understanding of the Universe or lead to targeted design of advanced materials. For example, today super-abrasive cubic Boron Nitride is used for grinding high-quality tool steels and artificial diamonds created using high temperature and high pressure are more prevalent than natural ones.

A team of scientists led by the University of Bayreuth has synthesized new materials at terapascal pressures using laser heating for the first time. The team used rhenium-nitrogen compounds as models to show that studies at pressures three times higher than pressure in the center of the Earth are now possible. Natalia Dubrovinskaya, professor at the University of Bayreuth and one of the corresponding authors of the paper, explains the relevance of these compounds: “These novel rhenium-nitrogen compounds showed that at ultra-high pressures we can make materials that cannot be made at lower pressures/temperatures, and uncover fundamental rules of physics and chemistry. We found, for example, that due to a huge compression, rhenium behaves chemically in a similar way to iron”.

Read more on the ESRF website

Image: Schematic illustration of the Diamond Anvil Cell assembly

Credit: Timofey Fedotenko

Tag: laser heating

Watching superheated silver nanoparticles bubbling

Scientists synthesise new materials at terapascal pressures for the first time