Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The proton precisely weighted

19.07.2017

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear Physics in Heidelberg did this not only just for fun or to set a new record. The proton is the nucleus of the hydrogen atom and building block in all other atomic nuclei. Therefore, the proton’s mass is an important parameter in atomic physics: Among other things it affects how the electrons move around the atomic nucleus.


Sketch of the Penning trap apparatus for measurement of the proton’s mass. Different voltages applied to the cylindrical electrodes (yellow) generate the trapping potential indicated by the red line.

This is reflected in the spectra, i.e., the light colours (wavelengths) atoms can absorb and emit again. By comparing these wavelengths with theoretical predictions, it is possible to test fundamental physical theories. Further, a precise comparison of the masses of the proton and the antiproton may help in the search for the crucial difference – besides the reversed sign of the charge – between matter and antimatter. This difference is tiny, but it has to exist, since the Universe practically completely consists of matter, although in the Big Bang matter and antimatter must have been created in equal amounts.

Penning traps are well-proven as suitable “scales” for ions. In such a trap, it is possible to confine single charged particles such as a proton nearly forever, by means of electric and magnetic fields. Inside the trap, the snared particle performs a characteristic motion that can be described by three frequencies. These frequencies can be measured and the mass of the particle calculated therefrom. In order to reach the targeted high precision, an elaborate measurement technique was required.

The carbon isotope 12C with a mass of 12 atomic mass units is defined as the mass standard for atoms. “We directly used it for comparison”, tells Sven Sturm. “First we stored each one proton and one carbon ion (12C6+) in separate compartments of our Penning trap apparatus, then transported alternately each one of the two ions into the central measurement compartment and measured its motion.” From the ratio of the two measured values one obtains the proton’s mass directly in atomic units. The measurement compartment is equipped with specifically developed purpose-built electronics. Andreas Mooser of RIKEN in Japan explains its function: „It allowed us to measure the proton under identical conditions as the carbon ion despite its about 12-fold lower mass and 6-fold smaller charge.”

The resulting mass of the proton of 1.007276466583(15)(29) atomic mass units is three times more precise than the presently recommended value. The numbers in parentheses refer to the statistical and systematic uncertainties, respectively.

However, the new value is significantly smaller than the current standard value. Measurements by other authors yielded discrepancies with respect to the mass of the tritium atom, the heaviest hydrogen isotope (T = 3H), and the mass of light helium (3He) compared to the “semiheavy” hydrogen molecule HD (D = 2H, deuterium, heavy hydrogen). “Our result contributes to solving this puzzle, since it corrects the proton’s mass in the proper direction”, says Klaus Blaum delightedly.

Florian Köhler-Langes of MPIK explains how the researchers intend to further improve the precision of their measurement: “In the future, we will store a third ion in our trap tower. By measuring simultaneously the motion of this reference ion, we will be able to eliminate the uncertainty originating from fluctuations of the magnetic field.”


Original publication:
High-precision measurement of the proton’s atomic mass
F. Heiße, F. Köhler-Langes, S. Rau, J. Hou, S. Junck, A. Kracke, A. Mooser, W. Quint, S. Ulmer, G. Werth, K. Blaum, and S. Sturm, Physical Review Letters 119, 033001 (18 July 2017 online) https://doi.org/10.1103/PhysRevLett.119.033001


Contact:

Prof. Dr. Klaus Blaum, MPI for Nuclear Physics
E-Mail: klaus.blaum@mpi-hd.mpg.de
Tel.: +49 6221 516850

Dr. Sven Sturm, MPI for Nuclear Physics
E-Mail: sven.sturm@mpi-hd.mpg.de
Tel.: +49 6221 516447

Dr. Andreas Mooser, RIKEN
E-Mail: andreas.mooser@cern.ch

Weitere Informationen:

https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.119.033001 - Physics Synopsis: Proton Loses Weight
https://www.mpi-hd.mpg.de/blaum/index.en.html - Division Blaum at MPIK
http://ulmerfsl.riken.jp/index.html - Ulmer Fundamental Symmetries Laboratory at RIKEN

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

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

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: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>