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Angular studies of photoelectrons in innovative research environments

Periodic Reporting for period 1 - ASPIRE (Angular studies of photoelectrons in innovative research environments)

Reporting period: 2016-03-01 to 2018-02-28

"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. In the ASPIRE network a series of novel experiments are being carried out that will combine and exploit these ideas and technologies to develop sensitive probes of evolving electronic structure.

The objectives of the ASPIRE project are:

• To bring together a unique team of internationally leading scientists to develop methods that enable the measurement of molecular frame photoelectron angular distributions from complex molecules through the following strands:
(a) Development and integration of laser and advanced light source techniques
(b) Development and integration of detection technologies

• To train and educate a cohort of ESRs who are creative and innovative in the development of novel instrumentation for advanced light sources such as free electron lasers and for the detection and discrimination of charged particles.

• To establish a unique unifying framework, facilitated by secondments and network-wide activities, for collaborative high impact research and training led by internationally leading scientists who are expert in each strand of the overall research objective.
Twelve ESRs were recruited to ASPIRE in the period September 2016 to March 2017 and all but one (who could not obtain a visa) attended the induction meeting in Aarhus in December 2016. During the first six months of their employment the ESRs concentrated on scientific and generic host-based training, subsequently moving into their individual research projects. The ESRs have their primary focus in one scientific work package, but are each involved in more than one scientific work package.

ESRs 1, 2, 4 and 6-9 have primarily been involved in work package 1. Work has included preliminary calculations of photoelectron angular distributions (ESR 1); synchrotron-based experiments on chiral molecules (ESR 2 and 4); measurements of PADs following the dissociative ionization of small molecules (ESR 4 and 6); measurements of PADs following the interaction of synchrotron radiation with amino acids (ESR 7); measurements of PAD following the ionization of small aromatic molecules that have been aligned by interaction with intense laser pulses (ESR 8); development of a new apparatus in which to perform experiments on molecules embedded in helium droplets (ESR 9); characterization of a new molecular beam required for low temperature experiments (ESR 10). It takes considerable time to analyse and interpret data from the technically complex experiments that have been undertaken in this work package, and analysis can only take place after a significant period of set up and characterisation of the necessary instrumentation. The output of publications is therefore primarily expected towards the later part of the ASPIRE project. At the present time there is one output (with ESR 2 as an author; this publication is related to deliverables 1.4 and 1.5 and underpins those deliverables), with one in preparation (with ESR 8 as an author; this publication finalises deliverable 1.1).

ESRs 11 and 12 have primarily been involved in work package 2, with contributions from ESRs 8 and 10. Work has included the development of a novel laser system (ESR 11); design of a new beamline (ESR 12); development of a new technique to create strongly field-free aligned molecules in helium nanodroplets (ESR 8); development of a new optical configuration for impulsive alignment and orientation of molecular samples (ESR 10). A paper describing the new laser system has been published, fulfilling deliverable 2.1. Unfortunately the originally recruited ESR 11 left the project in July 2017 following a mutual agreement with his supervisor.

ESRs 3 and 5, both of whom are based in companies, have primarily been involved in work package 3. Work has included the development of new detection software (ESR 3) and evaluation of a new detection system (ESR 5). The software developed by ESR 3 is the output promised for deliverable 3.1.

Various secondments have occurred both within and between work packages, including to partner organizations, and more are planned. A good team spirit has been developed between all of the ESRs through network meetings and online discussions and journal club. Joint publications are expected to emerge towards the end of the project.
The results described in the previous section are already moving the field beyond the current state-of-the-art, and all developments from now on are expected to do likewise. The measurements that are being made result from instrumental and theoretical developments that have been pioneered by the beneficiary organizations in ASPIRE. Three of the group leaders gave invited talks at the 2018 Gordon Conference on Photoionization and Photodetachment whose purpose is to define the state of the art. Good progress is being made towards all of the anticipated deliverables, with progress also being made towards a number of other, unforeseen, scientific publications. The major scientific goal will be the successful accomplishment of an experiment that involves the contributions of all the ESRs and will use new methods developed in ASPIRE to measure molecular-frame PADs from an amino acid. Such an experiment has not been attempted to date and there is no other team in the world that is in a position to conduct it. A further important goal remains the dissemination of highlights of the project to a broad audience and work on this has commenced through the instigation of blogs on the ASPIRE website which are contributed by the ESRs. The eventual societal impact 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.
ASPIRE Research Group at the ASPIRE Network Meeting Paris, September 2017