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 The magic wavelength of cadmium
16.09.2019 | University of Tokyo

nachricht Tomorrow´s coolants of choice
16.09.2019 | Helmholtz-Zentrum Dresden-Rossendorf

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: Happy hour for time-resolved crystallography

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.

The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.

Im Focus: Modular OLED light strips

At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.

Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...

Im Focus: Tomorrow´s coolants of choice

Scientists assess the potential of magnetic-cooling materials

Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....

Im Focus: The working of a molecular string phone

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Potsdam (both in Germany) and the University of Toronto (Canada) have pieced together a detailed time-lapse movie revealing all the major steps during the catalytic cycle of an enzyme. Surprisingly, the communication between the protein units is accomplished via a water-network akin to a string telephone. This communication is aligned with a ‘breathing’ motion, that is the expansion and contraction of the protein.

This time-lapse sequence of structures reveals dynamic motions as a fundamental element in the molecular foundations of biology.

Im Focus: Milestones on the Way to the Nuclear Clock

Two research teams have succeeded simultaneously in measuring the long-sought Thorium nuclear transition, which enables extremely precise nuclear clocks. TU Wien (Vienna) is part of both teams.

If you want to build the most accurate clock in the world, you need something that "ticks" very fast and extremely precise. In an atomic clock, electrons are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Society 5.0: putting humans at the heart of digitalisation

10.09.2019 | Event News

Interspeech 2019 conference: Alexa and Siri in Graz

04.09.2019 | Event News

AI for Laser Technology Conference: optimizing the use of lasers with artificial intelligence

29.08.2019 | Event News

 
Latest News

Novel mechanism of electron scattering in graphene-like 2D materials

17.09.2019 | Materials Sciences

Novel anti-cancer nanomedicine for efficient chemotherapy

17.09.2019 | Health and Medicine

Fungicides as an underestimated hazard for freshwater organisms

17.09.2019 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>