Infrared lasers reveal unprecedented details in surface scattering of methane

February 1, 2018, Ecole Polytechnique Federale de Lausanne
Illustration of methane scattering from a Ni(111) surface (left) and a diagram of the experimental setup used in this study (right). Credit: Rainer Beck/EPFL

When molecules interact with solid surfaces, a whole range of dynamic processes can take place. These are of enormous interest in the context of catalytic reactions, e.g. the conversion of natural gas into hydrogen that can then be used to generate clean electricity.

Specifically, the interaction of with catalyst such as nickel is of interest if we are to gain a detailed and meaningful understanding of the process on a molecular level. But studying scattering dynamics of polyatomic molecules such as methane has been challenging because current detection techniques are unable to resolve all the quantum states of the scattered molecules.

The lab of Rainer Beck at EPFL has now used novel infrared laser techniques to study methane scattering on a nickel surface for the first time with full resolution. Quantum-state resolved techniques have contributed much to our understanding of surface-scattering dynamics, but the innovation here was that the EPFL team was able to extend such studies to methane by combining infrared lasers with a cryogenic bolometer: a highly sensitive heat detector cooled to 1.8 K that can pick up the kinetic and internal energy of the incoming methane molecules.

In their experiments, a powerful infrared laser first pumps the incident into a single selected, vibrationally excited quantum state. A second laser combined with the bolometer is then used to analyze the quantum state distribution of the scattered molecules. With this approach, the scientists observed, for the first time, a highly efficient mechanism for vibrational energy redistribution during surface scattering.

The data from the study will allow state-of-the-art quantum theories for molecule/surface scattering to be tested stringently. Meanwhile, the new laser tagging technique introduced in this work is widely applicable and can be used to study many other polyatomic molecule/surface systems with unprecedented detail.

Explore further: Locating the precise reaction path: Methane dissociation on platinum

More information: Jörn Werdecker et al. Vibrational Energy Redistribution in a Gas-Surface Encounter: State-to-State Scattering of CH4 from Ni(111), Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.120.053402

Related Stories

Laser cooling a polyatomic molecule

April 26, 2017

(—A team of researchers at Harvard University has successfully cooled a three-atom molecule down to near absolute zero for the first time. In their paper published in Physical Review Letters, the team describes ...

Hot vibrating gases under the electron spotlight

December 12, 2017

Natural gas is used in refineries as the basis for products like acetylene. The efficiency of gaseous reactions depends on the dynamics of the molecules—their rotation, vibration and translation (directional movement). ...

Recommended for you

New thermoelectric material delivers record performance

January 17, 2019

Taking advantage of recent advances in using theoretical calculations to predict the properties of new materials, researchers reported Thursday the discovery of a new class of half-Heusler thermoelectric compounds, including ...

Zirconium isotope a master at neutron capture

January 17, 2019

The probability that a nucleus will absorb a neutron is important to many areas of nuclear science, including the production of elements in the cosmos, reactor performance, nuclear medicine and defense applications.

Mechanism helps explain the ear's exquisite sensitivity

January 16, 2019

The human ear, like those of other mammals, is so extraordinarily sensitive that it can detect sound-wave-induced vibrations of the eardrum that move by less than the width of an atom. Now, researchers at MIT have discovered ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.