A Simpler Method for Precise Molecular Orbital Visualisation
Published on : Friday 07-06-2024
Researchers report an innovative technique to analyse molecular dynamics and deformations in molecular films.
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Photoemission orbital tomography (POT) is a robust technique for precisely mapping the electron states within molecules, specifically identifying their molecular orbitals. However, conventional techniques are expensive and complex to use. Researchers from Chiba University, the University of Tsukuba, and Hiroshima City University have now developed a new POT method based on the PhaseLift algorithm that can accurately determine molecular orbitals in a single run, opening doors to a more efficient tool for monitoring molecular dynamics.
Discoveries and progress in materials science often lay the foundation for technological breakthroughs that reshape many industrial and commercial fields, including medicine, consumer electronics, and energy generation, to name a few. Yet, the development of experimental techniques crucially underpins the exploration of new materials, paving the way for groundbreaking discoveries. These techniques allow scientists to delve into a material's chemical and physical properties, unlocking insights essential for realising their potential applications.
In a recent study published in the Journal of Physical Chemistry A, a research team led by Associate Professor Kaori Niki from Chiba University, Japan, reported a new methodology to experimentally visualise molecular orbitals (MOs)—the distribution and state of electrons in a given molecule. Their latest paper, which was submitted on September 29, 2023, and published online on March 26, 2023, was co-authored by Ms Rena Asano and Prof Manabu Hagiwara from Chiba University, Prof Yoichi Yamada from the University of Tsukuba, and Prof Kazushi Mimura from Hiroshima City University.
The proposed method is centred on photoemission orbital tomography (POT). This technique consists of measuring the distribution and momentum of electrons released all around a material after absorbing energy from incoming light. By mapping these variables, one can then theoretically work out the MOs of the material. Despite being promising, traditional POT faces several challenges that greatly limit its applicability. First, multiple rounds of POT measurements are needed to probe the material at different photon energies and reconstruct three-dimensional MOs. This takes time and requires complex experimental protocols. Second, to properly account for differences in molecular orientation and deformations in a given material, it's necessary to combine POT with other analytical techniques, which is quite expensive and tedious. Third, traditional POT techniques are sensitive to noise in the measured data, which makes it difficult to observe small MOs.
To address all these limitations, Prof Niki's team developed a novel POT technique based on a mathematical analysis tool called the PhaseLift algorithm. This algorithm is designed to address a fundamental problem in signal and image processing: reconstructing a signal or image from incomplete or indirect measurements. Using PhaseLift, the researchers simplified the photoelectron momentum maps (PMMs) obtained through POT into a more manageable form, which in turn enabled them to more easily and accurately calculate the desired MOs.
One of the key advantages of the proposed approach is that precise MOs can be obtained from a single set of PMM measurements. Moreover, it is much better at handling noisy data. This is, in part, thanks to the clever use of sparsity-based techniques, which limits the space where solutions to MOs are considered to be only the most relevant molecular orbitals. Both theoretical analyses, as well as experimental tests, confirmed the validity of this innovative method, showcasing its potential. "This research was a collaboration between mathematicians, information theorists, and physical scientists and specifically included both experimentalists and theorists," explains Prof Niki. She further added, "Leveraging their expertise, we have achieved successful cross-disciplinary fusion research. This collaborative approach has enabled us to overcome previous challenges and deliver a POT method that holds promise for broader accessibility and applicability."
Using the proposed technique, scientists will be able to visualise the electronic states of molecules in thin film materials more easily. In turn, this will help better understand the origin of any relevant physical properties, leading to new smart material designs and further innovations in applied science. "Our developed method represents a breakthrough in the visualisation of the electronic states of materials that were previously challenging to observe," comments Prof Niki.
Recognising the immense potential that PhaseLift-based POT offers, Prof Niki and the team hope to become pioneers in this emerging research field. "In anticipation of the global spread of PMM, I hope that we can establish a center specialising in PMM analysis ahead of the rest of the world," she remarks, "This core institute will hopefully become a hub of innovation, driving the development of numerous new materials that will support the Japanese economy for the next half-century."
Let us wish them the best of luck in their future endeavors, and may their new experimental techniques bring about exciting technological advances!
Funding: This work was supported by the Grant-in-Aid for Scientific Research S (23H05492) and Scientific Research C (23K03841 and 20K05643) from the Japan Society for the Promotion of Science.
Reference
Title of original paper: Photoemission Orbital Tomography Using a Robust Sparse PhaseLift
Journal: Journal of Physical Chemistry A
DOI: 10.1021/acs.jpca.3c06506
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About Associate Professor Kaori Niki
Prof Kaori Niki obtained her PhD in Engineering from the University of Tokyo in 2008. She joined Chiba University in 2012, where she currently serves as Associate Professor. She specialises in nanotechnology and nanomaterials, with a particular focus on organic thin films, photoelectron spectroscopy, magnetic materials, artificial intelligence, and surface science. She has published over 20 peer-reviewed papers on these topics. She is also a member of the Japan XAFS Society, The Physical Society of Japan, and the Japan Society for Vacuum Surface Science.
Rockwell Automation expanding presence in India
Rockwell Automation, the world's largest company dedicated to industrial automation and digital transformation, recently announced plans to open a new manufacturing facility in Chennai, India. The 98,000-square-foot facility—with space for potential expansion—will help Rockwell build a more resilient, agile, and sustainable supply chain in the Asia Pacific region and around the globe.
India has the world's fifth-biggest and fastest-growing large economy. The country's economic policies will continue to have a significant impact on the global economy, particularly in the areas of trade, investment, and innovation. Rockwell is investing in India by expanding its manufacturing presence and building a new factory in Chennai. The facility will be located in the same industrial park as Rockwell's CUBIC manufacturing facility to help maximize supply chain resilience and create additional career opportunities for employees.
"We selected this location because we can create synergies with our existing CUBIC facility and increase agility and productivity in the region," said Dilip Sawhney, Managing Director - India, Rockwell Automation. "We're excited about building our presence in India, optimizing our manufacturing on a global scale, and enhancing the future of industrial operations in this growing market."
The facility in Chennai is expected to open in the first half of 2025 and will employ about 230 workers by the end of the year.
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