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Angular studies of photoelectrons in innovative research environments

Periodic Reporting for period 2 - ASPIRE (Angular studies of photoelectrons in innovative research environments)

Reporting period: 2018-03-01 to 2020-02-29

"The determination of chemical structure is vital in understanding the efficacy of medicines and materials and consequently underlies innovation. The equilibrium positions of atomic nuclei can be routinely determined by the technique of X-ray diffraction. However, this provides only partial information. In order to develop new medicines and materials it is necessary to understand bonding character and reactivity; these are determined by the energies and spatial distributions of electrons, the so-called ""electronic structure"". In order to investigate electronic structure, including the changes it undergoes during a chemical reaction, new probes are required. Whereas photoelectron spectroscopy (the emission of electrons caused by the interaction of molecules with UV light) has long been known to be sensitive to electronic structure, far more intimate details can be obtained by the measurement and analysis of the angles through which the photoelectrons are emitted. The information content of these angular measurements dramatically improves if measurements can be made relative to bonds in individual molecules. This is challenging because free molecules rotate, and measurements are therefore averaged over all the possible molecular orientations. Furthermore, a full characterization requires measurements to be made over a wide energy range. The combination of these requirements has severely limited the scope of most experiments to date. Recent technological developments are revolutionizing capabilities, bringing the exciting prospect of observing how electronic structure evolves in time. The ASPIRE ITN project was established to train 12 ESRs to capitalise on these recent technological breakthroughs and brings together a unique team of internationally leading scientists to develop methods that enable the measurement of molecular frame photoelectron angular distributions (MF-PADs) of complex molecules. The project has focused on the development and integration of new light source techniques and new detection technologies to pave the way for a new approach to electronic structure determination."
The ASPIRE project has formed a professional network across academia and industry which has been devoted to advancing state-of-the-art research in molecular structure determination through the measurement of molecular frame photoelectron angular distributions. The project was organised into three scientific work packages through which the recruited ESRs were assigned individual research projects requiring the collaboration with others in the network to achieve the project goals. This has resulted in the publication of 17 papers in leading scientific journals, with more in preparation. The ESRs completed an extensive training programme that not only developed their scientific skills but also developed their broader skill set and future career ambitions.

The first work package was explicitly focused on the goal of measuring molecular frame photoelectron angular distribution (PAD) from complex molecules. Progress in this work package was informed by technological developments made in work packages 2 and 3; this cross talk occurred through secondments of the ESRs. Six ESRs were primarily assigned to the delivery of this work package, with contributions from the other six ESRs. Their projects ranged from laser- and synchrotron-based experiments on chiral molecules; measurements of PADs following the dissociative ionization of small molecules; measurements of PAD following the ionization of molecules that have been aligned by interaction with intense laser pulses and development of a new apparatus in which to perform experiments on molecules embedded in helium droplets.

The second work package concerned the development and integration of laser and advanced light source techniques and two ESRs were primarily assigned to the delivery of this work package, with contributions from two of the ESRs primarily assigned to the first work package. The projects included the development of a novel laser system; the design of a new beamline; the development of a new technique to create strongly field-free aligned molecules in helium nanodroplets; and the development of a new optical configuration for impulsive alignment and orientation of molecular samples.

The third work package concerned the development and integration of detection technologies. This work was largely carried out in laboratories of the project's SME partners, Roentdek & Photek, by the two ESRs that had been recruited by these companies. Projects have included the successful development of new detection software and the evaluation of a new detection system. The ESR based at Photek has developed a multidimensional imaging detector and the technology will be incorporated in a commercial detector. This ESR will be staying on as a Photek employee to oversee the development of this new product.

Throughout the course of the ASPIRE project a strong sense of community has been developed both between the ESRs and with the scientists at the beneficiary and partner organisations. This sense of community has served to strengthen both scientific and professional collaborations. This has been assisted by regular secondments of ESRs to organizations within the network, and by regular network meetings (both physical and virtual). Team building formed an important activity at network meetings and was highly valued by the ESRs. The ESRs established online discussions and a journal club which they ran independently of their supervisors. They also contributed to outreach through the creation and dissemination of online blogs to communicate their research.
The results described above have moved the field of molecular structure determination beyond the state-of-the-art that existed at the start of the project. The measurements and data collected have resulted from developments in instrumentation and analysis that were pioneered by the beneficiary organizations in ASPIRE. Although the experimental work associated with ASPIRE is now complete, all of the participating research groups have manuscripts in preparation which will be submitted for publication later in 2020. Discussions between ESRs, supervisors and partner companies during network meetings has raised awareness of the needs and requirements for the next generation of instrumentation, increasing collaboration and understanding between academia and industry. The joint training and research programme, combined with the synergy of expertise in laser and synchrotron methods from academic and private sector beneficiaries and partners, has created a legacy of interactions among the network members which is expected to last for many years, enabling the partners to collaborate agilely in order to take advantage of future emerging technology.

Research leaders and ESRs have participated in and disseminated their research results at numerous national and international conferences which has enabled our research to contribute to the state-of-the-art and develop connections to other leading international research teams in the field. We have sought to disseminate the highlights of the ASPIRE project to the general public through blogs written by the ESRs and hosted on the ASPIRE website. The eventual societal impact of the research in terms of the design of new medicines and materials is extremely long term and expected to occur long after the conclusion of this project.