Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Frozen highly-charged ions for highest precision spectroscopy

13.03.2015

A team of researchers from the Max Planck Institute for Nuclear Physics in Heidelberg, the Physikalisch-Technische Bundesanstalt in Braunschweig and the University of Aarhus in Denmark demonstrated for the first time Coulomb crystallization of highly-charged ions (HCIs). Inside a cryogenic radiofrequency ion trap the HCIs are cooled down to sub-Kelvin temperatures by interaction with laser-cooled singly charged Beryllium ions. The new method opens the field of laser spectroscopy of HCIs providing the basis for novel atomic clocks and high-precision tests of the variability of natural constants. [Science, March 13 2015]

Atoms can lose many of their electrons at very high temperatures, forming highly-charged ions (HCIs). Such HCIs constitute a large class of atomic systems offering various new possibilities for high precision studies in metrology, astrophysics, and even for the search for new physics beyond the Standard Model of particle physics.


Figure 2: CCD images of Be+ ion crystals in the CryPTEx Paul trap.

Graphics: MPI für Kernphysik


Figure 1: The experimental set-up for production, trapping and cooling for highly-charged ions (HCIs, here Ar13+).

Graphics: MPI für Kernphysik

Over the last few decades, laser spectroscopy of cold atoms or low-charge state ions has developed into today’s most powerful method for high-precision measurements. However, this was so far restricted to a few atomic and ionic species, and the preparation of cold HCIs constituted a major challenge in atomic physics up to now.

The main obstacle arises from the usual production methods for HCIs, which require high temperatures of millions of degrees. But in order to exploit the power of laser spectroscopy, temperatures of less than one degree above absolute zero have to be reached; i. e. the thermal energy of the ions has to be reduced by a factor of at least 10 million.

In a joint project by the Max Planck Institute for Nuclear Physics Heidelberg (MPIK), the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig and Aarhus University, a team of physicists succeeded in cooling HCIs down to sub-Kelvin temperatures and freezing their motion in vacuum forming a so-called Coulomb crystal.

The procedure was demonstrated for the first time at MPIK in the group under José Crespo López-Urrutia. It involves three steps (Fig. 1), explains PhD student Lisa Schmöger, who built the deceleration set-up and carried out the reported experiment: First, HCIs are generated in Hyper-EBIT, an ion source which produces and confines ions at a million degrees temperature inside a dense and energetic electron beam in an extreme vacuum (1).

Bunches of HCIs are then extracted from this trap, transferred through a vacuum beamline, slowed down and pre-cooled with a pulsed linear deceleration potential (2). The ions are very delicately transported into, and eventually confined in, CryPTEx, a cryogenic radiofrequency Paul trap developed at the MPIK in collaboration with Michael Drewsen’s group in Aarhus (3).

Inside this trap, the HCIs bounce back and forth between mirror electrodes, slowly losing speed before they become embedded in a laser-cooled ensemble of light ions (singly-charged beryllium) which provide a cooling bath for the HCIs (providing so-called indirect or sympathetic cooling).

In a radiofrequency trap, the confined, mutually repelling ions are forced to share a small volume in space by a combination of electrostatic and oscillating electric fields inside a vacuum chamber. Additionally, the millimeter-sized beryllium ion cloud is cooled by a special laser such that the ions freeze out and form a Coulomb crystal once their thermal motion becomes negligible compared with their electric repulsion.

Sophisticated laser systems built at the PTB by Oscar Versolato and colleagues are used at MPIK for this purpose. Once sufficiently cold inside the laser cooled ion ensemble, the HCIs crystallize as well, and can be stored in various configurations. The image displayed in Fig. 2a shows the pure beryllium crystal consisting of about 1500 ions imaged by a CCD camera which detects the fluorescence light emitted by each individual ion due to the laser cooling.

In Fig. 2b five trapped Ar13+ ions appear as a chain of dark “holes” since they do not shine themselves, but repel the surrounding beryllium ions. Fig. 2c depicts a crystal of 29 beryllium ions with a single Ar13+ ion in the centre. The extreme case of only two remaining ions (one of each species) is demonstrated in Fig. 2d (with the invisible Ar13+ ion in the centre).

Such ion pairs form the basis for quantum clocks and quantum logic spectroscopy, a technique developed by Piet Schmidt, the PTB group leader during his stay at Nobel laureate Dave Wineland’s laboratory at NIST (Boulder, USA). Here, the “spectroscopy ion” provides a high-precision optical transition used to keep the pace of the clock at 17 decimal digits accuracy. It is quantum mechanically linked to the “logic ion” which serves both for the cooling and readout of the spectroscopy ion: laser pulses enable the fluorescing logic ion to feel the quantum state of its nearly undetectable neighbour and changes strongly its own fluorescence yield according to the excitation of the other. José Crespo López-Urrutia explains with an analogy: “In this quantum married couple, the ions feel everything together, but whilst one of the partners cannot talk at all, the other one talks a lot. You then simply ask the talkative one.”

The efficient cooling of trapped HCIs opens up new fields in laser spectroscopy: precision tests of quantum electrodynamics, measurement of nuclear properties, and laboratory astrophysics. HCIs are rather insensitive to thermal radiation shifts and other systematic effects that could make a clock imprecise, and thus promise future applications for novel optical clocks using quantum logic spectroscopy.

The ultimate goal of the MPIK-PTB collaboration will be to test the time dependence of natural constants such as the fine structure constant α, which determines the strength of electromagnetic interaction. For laser spectroscopy, theory predicts that the most sensitive atomic species with respect to α variation is 17-times ionized iridium. In preparation for these future studies, a new highly stable laser system will be installed by the PTB at MPIK to demonstrate the technique with the better known Ar13+ first. And the young scientists seem very eager to start playing with this tool and their novel cooling method.

Original paper:

Coulomb crystallization of highly charged ions
L. Schmöger, O. O. Versolato, M. Schwarz, M. Kohnen, A. Windberger, B. Piest, S. Feuchtenbeiner, J. Pedregosa-Gutierrez, T. Leopold, P. Micke, A. K. Hansen, T. M. Baumann, M. Drewsen, J. Ullrich, P. O. Schmidt, J. R. Crespo López-Urrutia
Science, 13. März 2015 10.1126/science.aaa2960

Contact:

Lisa Schmöger
MPI für Kernphysik
Phone: +49 6221 516-331
E-mail: lisa.schmoeger@mpi-hd.mpg.de

Dr. José R. Crespo-López Urrutia
MPI für Kernphysik
Phone: +49 6221 516-521
E-mail: jose.crespo@mpi-hd.mpg.de

Prof. Dr. Piet O. Schmidt
QUEST Institute for Experimental Quantum Metrology
Physikalisch-Technische Bundesanstalt
Phone: +49 531 592 4700
E-mail: piet.schmidt@ptb.de

Prof. Dr. Michael Drewsen
The Ion Trap Group
QUANTOP - Danish National Research Foundation's Center for Quantum Optics
Department of Physics and Astronomy, Aarhus University
Phone: +45 8715 5679
E-mail: drewsen@phys.au.dk

Weitere Informationen:

http://www.mpi-hd.mpg.de/pfeifer/page.php?id=36 EBIT Group, MPIK

http://www.quantummetrology.de/quest/eqm/cetest-firstpage.html Quantum Logic Spectroscopy, PTB

http://phys.au.dk/en/research/research-areas/amo/the-ion-trap-group/ Ion Trap Group, U Aarhus

Dr. Bernold Feuerstein | Max-Planck-Institut für Kernphysik

More articles from Physics and Astronomy:

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

nachricht Magnetic moment of a single antiproton determined with greatest precision ever
19.01.2017 | Johannes Gutenberg-Universität Mainz

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: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>