Tag: Universe

On the hunt for axions

On the hunt for axions

New X-ray experiment at the European XFEL could solve some of the mysteries of physics

Researchers at European XFEL, together with colleagues from the UK Science and Technology Facilities Council (STFC), the University of Oxford and other research institutions, have been searching for a hypothetical particle that could potentially explain the dark matter of the universe. The experiment is described in a study published in Physical Review Letters.

The researchers hunted for so-called axions at the High Energy Density instrument HED/HiBEF at European XFEL. Axions are tiny and incredibly light hypothetical particles. They are intended to explain, for example, why neutrons, which make up atomic nuclei alongside protons, have no electric dipole moment, even though the nuclear building blocks consist of even smaller charged particles known as quarks. This could also be an indication of new physics beyond the standard model. Furthermore, axions are a natural candidate for dark matter, the mysterious substance that makes up most of the structure of the universe.

The researchers used European XFEL in Schenefeld near Hamburg, the largest and most powerful X-ray laser in the world for their experiments. They channelled the intense X-ray beam of European XFEL through thin plates of germanium crystals. These have strong electric fields inside. For moving particles, this appears like an extremely strong magnetic field of around 1000 Tesla. This enables photons to transform themselves into axions and back again.

Read more on the European XFEL website

Image: Axion search at the HED/HiBEF instrument of European XFEL

Credit: European XFEL

How football-shaped molecules occur in the universe

How football-shaped molecules occur in the universe

For a long time it has been suspected that fullerene and its derivatives could form naturally in the universe. These are large carbon molecules shaped like a football, salad bowl or nanotube. An international team of researchers using the Swiss SLS synchrotron light source at PSI has shown how this reaction works. The results have just been published in the journal Nature Communications.

“We are stardust, we are golden. We are billion-year-old carbon.” In the song they performed at Woodstock, the US group Crosby, Stills, Nash & Young summarised what humans are essentially made of: star dust. Anyone with a little knowledge of astronomy can confirm the words of the cult American band – both the planets and we humans are actually made up of dust from burnt-out supernovae and carbon compounds billions of years old. The universe is a giant reactor and understanding these reactions means understanding the origins and development of the universe – and where humans come from.

In the past, the formation of fullerenes and their derivatives in the universe has been a puzzle. These carbon molecules, in the shape of a football, bowl or small tube, were first created in the laboratory in the 1980s. In 2010 the infrared space telescope Spitzer discovered the C60 molecules with the characteristic shape of a soccer ball, known as buckyballs, in the planetary nebula Tc 1. They are therefore the biggest molecules to have been discovered to date known to exist in the universe beyond our solar system.

But how do they actually form there? A team of researchers from Honolulu (USA), Miami (USA) and Tianjin (China) has now completed an important reaction step in the formation of the molecules, with active support from PSI and the vacuum ultraviolet (VUV) beamline of the synchrotron light source Swiss SLS. “PSI offers unique experimental facilities and that’s why we decided to collaborate with Patrick Hemberger at PSI,” says Ralf Kaiser from the University of Hawaii in Honolulu, the leading international researcher in this field.

Read more on the PSI website

Credit: Shane Goettl/Ralf I. Kaiser

Scientists synthesise new materials at terapascal pressures for the first time

Scientists synthesise new materials at terapascal pressures for the first time

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