Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Unveiling the key polyatomic ion of interstellar chemistry

In the chemistry of interstellar clouds, the three-atomic hydrogen ion plays a key role. In these reactions, also simple organic molecules form.

Although H3+ is the simplest polyatomic molecular ion, its vibrational spectrum at high excitations to date has been neither experimentally precisely known nor theoretically understood. Precise measurements at the Max Planck Institute for Nuclear Physics in Heidelberg now provided the decisive hints on how to dramatically improve the quantum theoretical calculations. (Physical Review Letters 108, 023002 (2012))

Laser spectroscopy of triatomic hydrogen ions is performed at the MPI for Nuclear Physics at temperatures near -210°C in this cryogenic ion trap, a 22-pole cage further developed from the original design by D. Gerlich at the University of Freiburg, Germany. Photo: MPIK, O. Novotný

Two examples of the quantum mechanical wave functions for the atomic nuclei in H3+ at high excitation (corresponding to the 6th and 7th harmonics of the bending vibration in (a) and (b), respectively). They are taken from results of the new calculations (electronic supplement of the paper in Physical Review Letter). The square of this function yields the probability density of locating the atomic nuclei relative to each other. The wave functions show a high probability density for linear configurations of H3+, extremely far away from the equilateral triangular structure of non-vibrating H3+. With the new theory such configurations can be described exactly. Graph: Authors of the paper

Within a molecule, the binding cloud allocates stable positions to the atomic nuclei and determines the frequencies at which they can oscillate around these positions. Ground and overtone frequencies of these vibrations give a fingerprint of the molecular structure and reveal how the electron cloud can resist to deformations of the molecule. The frequencies of very weak high-overtone oscillations must be measured to understand the molecular forces at large deformations. Even for the most basic neutral molecule H2, experiments and quantum calculations needed long time to reach precise agreement; this was reached about three decades ago.

Adding another proton to H2 yields H3+, the simplest polyatomic ion. With just the single additional proton added, challenges rise enormously, both for measuring the weak high-overtone vibration frequencies and for accurately calculating them by quantum theory. Although H3+ is an abundant and chemically very active molecular ion in interstellar space, it can be produced in the laboratory only under extremely dilute conditions, mostly in plasmas. Moreover, in the plasma environment where H3+ ions mostly occur, their temperatures are very high and lead to an essentially impenetrable forest of possible frequencies at which vibrations of these ions can be excited. Finally, only undeformed cold H3+ has a highly symmetrical triangular shape, while all types of asymmetric triangular and even linear shapes occur if it is strongly deformed.

These challenges were successfully met by a recent experiment at a cryogenic buffer gas ion trap at the MPIK, where since some years H3+ ions can be cooled down to only -210 °C for precise laser spectroscopy. In the new experiments, visible light was employed to put the ions into vibration instead of the infrared radiation used earlier, and vibrations up to the eighth overtone – extremely weak resonances – could be excited. After long searches in large intervals around inaccurately predicted transition frequencies, the scientists for the first time could find overtone excitation lines extending far into the visible spectral range.

The new precisely measured overtone frequencies gave decisive hints to an international group of molecular theorists on how to dramatically improve their first-principles quantum calculations of this fundamental triatomic molecule. The new measurements and quantum calculations now for the first time show precise agreement between each other up to strong deformations for a polyatomic molecule, similar to that obtained for the diatomic hydrogen molecule H2 about thirty years ago.

Original publication:
“Precision measurements and computations of transition energies in rotationally cold triatomic hydrogen ions up to the mid-visible spectral range”
M. Pavanello et al., Physical Review Letters 108, 023002 (2012).
doi: 10.1103/PhysRevLett.108.023002

Dr. Bernold Feuerstein | Max-Planck-Institut
Further information:

More articles from Physics and Astronomy:

nachricht Light-driven atomic rotations excite magnetic waves
24.10.2016 | Max-Planck-Institut für Struktur und Dynamik der Materie

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

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: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Oasis of life in the ice-covered central Arctic

24.10.2016 | Earth Sciences

‘Farming’ bacteria to boost growth in the oceans

24.10.2016 | Life Sciences

Light-driven atomic rotations excite magnetic waves

24.10.2016 | Physics and Astronomy

More VideoLinks >>>