Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Rapid water formation in diffuse interstellar clouds


Two important steps in the gas-phase formation of water in diffuse interstellar clouds proceed faster than previously assumed. This is the result of measurements at low temperatures, performed by researchers at the MPI for Nuclear Physics in Heidelberg. Complementary calculations, using a novel method that takes quantum effects into account, are in excellent agreement. The combined results have far-reaching implications for the understanding of interstellar chemistry and the theoretical treatment of low-temperature reactions.

Accumulations of gas and dust in space can be observed with telescopes as interstellar clouds. Despite the low temperatures and densities, a rich variety of molecules has been found in these environments. The backbone of the cold interstellar chemistry is a network of reactions between charged and uncharged atoms or molecules, so-called ion-neutral reactions.

Simplified interstellar chemistry network, showing the gas-phase water formation chain (blue) in front of the Orion nebula.

MPI für Kernphysik / background: NASA

Overview of the experimental setup, with the cryogenic 22-pole ion trap in the center.

MPI für Kernphysik

In today´s universe, ion-neutral reactions in the gas phase can lead to the production of complex molecules, from protonated water (H₃O⁺) to organic compounds. When one of the protonated and therefore positively charged molecules encounters an electron, it can be neutralized and usually breaks up into neutral fragments. This process leads to the formation of neutral molecules in space, ranging from water (H₂O) to more complex species, like alcohol and other organics.

But how effective are these processes? To answer this question, it is crucial to find out how often a collision between the reaction partners at low temperature actually leads to a chemical reaction, because collisions are rare in the thin medium. To shed light on these processes, laboratory experiments have to be performed under true interstellar conditions. As these conditions are difficult to realize, present astrochemical models are mostly based on data that have been measured at much higher temperatures and densities, and accordingly are only of limited validity.

Water forms in diffuse interstellar clouds – where reactions on the surface of interstellar dust play a minor role – via a chain of processes started by cosmic rays. Intermediate products are the hydroxyl ion (OH⁺) and the water cation (H₂O⁺), which both react with hydrogen molecules, attaching one hydrogen atom and releasing the other one. The ERC-funded ‘Astrolab’ group of Holger Kreckel at the MPI for Nuclear Physics succeeded to measure the reaction rates of these two important steps in the gas-phase formation of interstellar water at low temperatures.

The scientists trapped the ions in a cryogenic radiofrequency ion trap, in which temperatures down to 10 degrees above absolute zero are accessible. Up to 100 milliseconds after adding a defined amount of hydrogen gas, they determined how many of the initial ions were still present. From the data, they derived so-called rate coefficients for both reactions, which are a measure of the efficiency of the reactions between the collision partners. It turned out that in both cases practically every collision leads to a chemical reaction.

In parallel, colleagues from Cyprus and the USA performed theoretical calculations using a novel method. In an elegant way, this approach employs analogies between quantum systems and the properties of ring-shaped molecules to account for quantum effects which are particularly relevant at low temperatures. The calculated rate coefficients are in excellent agreement with the measured values.

Compared to previous measurements at room temperature, the new values are considerably “faster”. This has implications for the understanding of interstellar chemistry, reaching far beyond the water formation chain. “Our results show once again that it is imperative to use rate coefficients that have been measured under interstellar conditions for astrochemical models“, says Holger Kreckel.

“Since this is experimentally often difficult and time-consuming, it is also important to develop theoretical procedures that can cope with quantum effects which are relevant for low-temperature processes, and to benchmark them with measurements. In this case, the strength of our work lies in the combination of experimental and theoretical methods that are appropriate for interstellar conditions.“

Low temperature rates for key steps of interstellar gas-phase water formation
Sunil S. Kumar, Florian Grussie, Yury V. Suleimanov, Hua Guo, Holger Kreckel
Science Advances 4, eaar3417 (2018) doi: 10.1126/sciadv.aar3417

Dr. Holger Kreckel
Stored and Cooled Ions Division, Professor. Dr. Klaus Blaum
Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Tel.: +49 6221 516 517

Weitere Informationen: - Astrolab group homepage at the MPI for Nuclear Physics

Dr. Gertrud Hönes | Max-Planck-Institut für Kernphysik

More articles from Physics and Astronomy:

nachricht SLAC's high-speed 'electron camera' films molecular movie in HD
17.04.2019 | DOE/SLAC National Accelerator Laboratory

nachricht Light from exotic particle states
16.04.2019 | Vienna University of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

Im Focus: Newly discovered mechanism of plant hormone auxin acts the opposite way

Auxin accumulation at the inner bend of seedling leads to growth inhibition rather than stimulation as in other plant tissues.

Increased levels of the hormone auxin usually promote cell growth in various plant tissues. Chinese scientists together with researchers from the Institute of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

Latest News

CubeSats prove their worth for scientific missions

17.04.2019 | Information Technology

Neuron and synapse-mimetic spintronics devices developed

17.04.2019 | Power and Electrical Engineering

Better healing for eardrum injuries? - new adhesive structures for medical applications

17.04.2019 | Life Sciences

Science & Research
Overview of more VideoLinks >>>