Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Creation of coherent states in molecules by incoherent electrons

23.10.2017

In a breakthrough experiment using a novel negative ion momentum imaging technique, researchers from Tata Institute of Fundamental Research, Mumbai India and Open University, Milton Kyenes, UK have shown -- for the first time -- that incoherent electrons displaying their quantum mechanical nature, can induce coherence in molecular systems on attachment.

Their latest results published in the Journal, Nature Physics (DOI: 10.1038/nphys4289), show that the coherence induced by the capture of single electron by H2 molecule results in the ejection of H? ion in preferentially backward direction with respect to the incoming electron beam.


Momentum images of H from H2 and D from D2 at different electron energies. The one at 4 eV for H is symmetric, while those above 14 eV are strongly asymmetric. The asymmetry in D is less pronounced and appear to change direction with change in electron energy.

Credit: E. Krishnakumar et al, Nature Physics

The other product of the dissociation is the H-atom in its excited state. In other words, this coherence induced in the molecule segregates the charge and excess energy in the system in a preferred manner. Similar measurements in the isotopomer of H2 namely D2 does not show such a strong asymmetry in ejection of the fragment ion but shows the reversal of the asymmetry as a function of incoming electron energy.

So far researchers have used such coherence induced by laser beams to control molecular dissociation and have considered it as the basis for possible control of chemical reactions using photons. But in that case, the coherence in the resulting excited molecular entity is understood to stem from the absorbed laser radiation. By demonstrating the presence of such coherence resulting from a capture of an incoherent electron, Prof. Krishnakumar and co-workers have shown that such coherence can also stem from the transfer of more than one value of angular momentum quanta.

On the capture of a low energy electron, a relatively unstable molecular negative ion is formed. Subsequently, this negative ion decays by ejecting the extra electron. However, if the ion survives against the electron ejection, it undergoes dissociation.

This is known as dissociative attachment. According to Prof. Krishnakumar, dissociative attachment is traditionally linked with transfer of multiple values of angular momentum quanta in the molecular system. However, it is for the first time such a quantum coherent response has been observed from a molecule.

Low energy electrons are ubiquitous and are known to play important role in variety of phenomena relevant to astrochemistry (where they participate in synthesis of new molecules), in radiation biology (where they cause chemical changes in living cell, plasma chemistry), atmospheric chemistry, radioactive waste management and nanolithography -- to name but a few.

In all these cases, dissociative attachment plays a critical role. The unstable excited molecular negative ion states are at the core of this process. However, due to very short lifetime of these species very little is known about them at present.

The group led by Prof. Krishnakumar and Dr. Prabhudesai in TIFR has pioneered research on several aspects of low energy electron interactions with molecules in gas and condensed phase with particular emphasis on the possibility of controlling chemical reactions using low energy electrons.

These new results point to rich unexplored dynamics of excited molecular negative ions that might open up new possibilities in inducing chemical control. They also pose a challenge to theoreticians to come up with a detailed model for the negative ion chemistry that is associated with low energy free electron scattering.

These measurements were carried out by Prof. Krishnakumar using an experiment built by him at the Open University in UK, where he was on invitation as a Marie Curie Professor to help build a novel electron scattering experiment for the European scientists, similar to the one he had conceived and built at TIFR. Dr. Prabhudesai and Prof. Krishnakumar provided the interpretation of the data along with the model.

Media Contact

E. Krishnakumar
ekkumar@tifr.res.in
91-986-901-3407

http://www.tifr.res.in 

E. Krishnakumar | EurekAlert!

More articles from Physics and Astronomy:

nachricht Structured light and nanomaterials open new ways to tailor light at the nanoscale
23.04.2018 | Academy of Finland

nachricht On the shape of the 'petal' for the dissipation curve
23.04.2018 | Lobachevsky University

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: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Complete skin regeneration system of fish unraveled

24.04.2018 | Life Sciences

Scientists create innovative new 'green' concrete using graphene

24.04.2018 | Materials Sciences

BAM@Hannover Messe: innovative 3D printing method for space flight

24.04.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>