Fs-VUV Generation: Mapping the Reaction Co-ordinate in Photochemical Dynamics

Lead Research Organisation: Heriot-Watt University
Department Name: Sch of Engineering and Physical Science

Abstract

Developing a detailed understanding of how molecules interact with light is of great importance. For example, it is particularly relevant to fundamental processes that take place in biology, such as vision and photosynthesis, as well as in so-called "self-protection" mechanisms that occur in both DNA and the melanin pigmentation system, serving to protect the body from the potentially damaging effects of ultraviolet (UV) light. Additionally, an understanding of light-molecule interactions is of critical relevance for many other classes of molecules, including photostabilizers, photochromic polymers, molecular switches, light harvesting complexes and drugs for the targeted delivery of active agents (photodynamic therapy). Developing refined experimental techniques to enhance the study of such systems is therefore an important challenge.

The use of "ultrafast" femtosecond (fs) laser pulses with temporal durations comparable to the timescales of molecular motion (1 fs = 10^-15 s) is a powerful method for studying light-matter interactions. Energy redistribution within a molecule following the absorption of light may be followed in real time using "pump-probe" techniques: the pump initiates the energy redistribution process (effectively starting a dynamical "clock") and the system may then be interrogated at a series of precisely controlled delay times by the probe - mapping out the pathways for energy flow. However, a key limitation with this approach is that, in many instances, the full "view" along these pathways is restricted, obscuring critical information. Addressing this issue forms one of the main goals of this work.

The proposed research programme brings together a team of investigators with a unique set of complementary skills and experience in ultrafast lasers, non-linear optics, molecular spectroscopy and dynamics, ultra-high vacuum science and cutting edge computational methods. In the initial phase, we will develop an economic and compact light source that will produce femtosecond light pulses across the vacuum-ultraviolet (VUV) region of the electromagnetic spectrum. This will expand on recently developed experimental methods. The source output (which we refer to as fs-VUV) is well suited for use as the probe step in pump-probe experiments as it provides a highly expanded view of the pathways that facilitate excess energy redistribution in many molecules (when compared to using non-VUV probes). This will yield previously unobtainable levels of insight into the nature of light-molecule interactions.

Following the successful development and characterization of the fs-VUV source, it will then be used to upgrade an existing experiment at Heriot-Watt University that uses pump-probe photoelectron imaging as a technique to study the dynamics of energy redistribution. In the next phase of the project we will use the fs-VUV probe to investigate energy redistribution in urocanic acid. This is one of the primary UV absorbers present in the skin (possibly acting as a natural "sunscreen") and our experimental results, in conjunction with supporting theoretical work, will yield important new mechanistic information relating to this important biomolecular system.

In the final phase of the project, we will use the fs-VUV as a probe in photoelectron imaging experiments that investigate energy redistribution and molecular fragmentation in nitrobenzene and some of its selected derivatives. These are important test systems for the development of improved drugs for photodynamic therapy. In particular, we will investigate the product channel leading to light-induced release of nitric oxide (NO), which is important for the regulation and maintenance of many physiologically vital functions. Our work will begin to develop improved understanding of the general mechanistic principles that enhance the NO production channel and should be readily scalable to larger, practically applicable systems.

Planned Impact

The proposed work is fundamental in nature and it is therefore expected that the economic and societal benefits stemming from the research output will primarily be realized in the longer term. This is in addition to the academic benefits, which will be much more immediate. Our research will significantly advance existing methodologies for the study of energy redistribution within the excited states of molecular systems with biological and medical relevance, yielding important new mechanistic insight. This has potential implications for a wide range of practical applications where the interplay between structure and dynamics influences light-matter interactions and associated chemical or biological function. In addition, the tuneable fs-VUV source we will develop will also be of possible interest to the applied photonics community. In order to facilitate timely uptake of our findings we will exploit a wide variety of routes to maximize exposure to relevant parties. These include presenting our work at large, interdisciplinary conferences that attract several thousand delegates as well as making use of well-established industry-academia networking events at the local, national and European levels. These networking events span a number of different themes: from exploratory collaboration between universities and companies, to forums discussing policy roadmaps for major funding initiatives. It is critical for the continuity and timeliness of any follow-up research that such opportunities are fully exploited throughout the duration of the project, rather than simply at its conclusion.

There will, in addition, be very immediate impact stemming from our work in the form of highly trained personnel with technical skills in the use of cutting edge laser, non-linear optics, vacuum, spectroscopic, data analysis and theoretical techniques. They will also have well-developed generic and widely transferable communication, presentation and problem solving skills. They will, therefore, be ideally positioned to contribute to the growth or creation of new research projects (both pure and applied) as well as high-tech companies, enhancing innovative capacity and possible revenue generation.

Enhanced public awareness and engagement with our research efforts will be achieved through consciously non-specialist postings on university web pages, university open days and via video reports that will be produced at regular intervals throughout the project and made available in the public domain. It is anticipated that these video reports will also be beneficial for attracting future research students to the key areas of ultrafast lasers and optics, molecular spectroscopy and dynamics, and theoretical photochemistry. The video will also advertise the existence of the project to interested parties in the commercial sector.
 
Description EPSRC Grant
Amount £588,864 (GBP)
Funding ID EP/R030448/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2018 
End 10/2021
 
Description Denmark 
Organisation University of Copenhagen
Country Denmark 
Sector Academic/University 
PI Contribution Provided experimental infrastructure to perform experiments. Also provided training for visiting PhD student
Collaborator Contribution Provided PhD student to visit for 3 months to gain experience using my set-up
Impact J. O. F. Thompson, L. B. Klein, T. I. Sølling, M. J. Paterson & D. Townsend, The role of novel Rydberg-valence behaviour in the non-adiabatic dynamics of tertiary aliphatic amines, Chem. Sci., 7, 1826, (2016). Liv B. Klein, Thorbjørn J. Morsing, Ruth A. Livingstone, Dave Townsend & Theis I. Sølling, The effects of symmetry and rigidity on non-adiabatic dynamics in tertiary amines: A time-resolved photoelectron velocity-map imaging study of the cage-amine ABCO, accepted Phys. Chem. Chem. Phys. (2016).
Start Year 2013
 
Description HWU (MJP) 
Organisation Heriot-Watt University
Country United Kingdom 
Sector Academic/University 
PI Contribution Experimental measurements investigating energy redistribution in model biological systems
Collaborator Contribution Theoretical calculations to assist in data interpretation
Impact R. A. Livingstone, J. O. F. Thompson, M. Iljina, R. J. Donaldson, B. J. Sussman, M. J. Paterson & D. Townsend, Time-resolved photoelectron imaging of excited state relaxation dynamics in phenol, catechol, resorcinol and hydroquinone, J. Chem. Phys., 137, 184304, (2012). A. S. Chatterley, J. D. Young, D. Townsend, J. M. Žurek, M. J. Paterson, G. M. Roberts & V. G. Stavros, Manipulating dynamics with chemical structure: probing vibrationally-enhanced tunnelling in photoexcited catechol, Phys. Chem. Chem. Phys., 15, 6879, (2013). J. O. F. Thompson, L. Saalbach, S. W. Crane, M. J. Paterson & D. Townsend, Ultraviolet relaxation dynamics of aniline, N, N-dimethylaniline and 3,5-dimethylaniline at 250 nm, J. Chem. Phys., 142, 114309, (2015). M. M. Zawadzki, J. O. F. Thompson, E. A. Burgess, M. J. Paterson & D. Townsend, Time-resolved photoionization spectroscopy of mixed Rydberg-valence states: indole case study, Phys. Chem. Chem. Phys., 17, 26659, (2015). J. O. F. Thompson, L. B. Klein, T. I. Sølling, M. J. Paterson & D. Townsend, The role of novel Rydberg-valence behaviour in the non-adiabatic dynamics of tertiary aliphatic amines, Chem. Sci., 7, 1826, (2016). Interdisciplinary: Chemistry/Physics
Start Year 2011
 
Description NRC & University of Ottawa 
Organisation National Research Council of Canada
Country Canada 
Sector Public 
PI Contribution PhD student form my group (Ruth Livingstone) undertook a series of experiments at NRC under the supervision of Prof. Albert Stolow (U. Ottawa) and Dr Ben Sussman (NRC). This lead to data that was published following analysis lead by us. More recently (2016) a second PhD student in my group (Magdalena Zawadzki) made a similar visit.
Collaborator Contribution Provided technical infrastructure to undertake experiments and provided training for PhD student
Impact R. Livingstone, O. Schalk, A. E. Boguslavskiy, G. Wu, L. T. Bergendahl, A. Stolow, M. J. Paterson & D. Townsend, Following the relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy, J. Chem. Phys., 135, 194307, (2011). R. A. Livingstone, J. O. F. Thompson, M. Iljina, R. J. Donaldson, B. J. Sussman, M. J. Paterson & D. Townsend, Time-resolved photoelectron imaging of excited state relaxation dynamics in phenol, catechol, resorcinol and hydroquinone, J. Chem. Phys., 137, 184304, (2012). Multi-disciplinary - Physics & Chemsitry
Start Year 2009
 
Description Warwick 
Organisation University of Warwick
Country United Kingdom 
Sector Academic/University 
PI Contribution Conducted gas-phase experiments as part of a joint experimental undertaking
Collaborator Contribution Conducted solution-phase experiments as part of joint experimental undertaking
Impact A. S. Chatterley, J. D. Young, D. Townsend, J. M. Žurek, M. J. Paterson, G. M. Roberts & V. G. Stavros, Manipulating dynamics with chemical structure: probing vibrationally-enhanced tunnelling in photoexcited catechol, Phys. Chem. Chem. Phys., 15, 6879, (2013). S. E. Greenough, M. D. Horbury, J. O. F. Thompson, G. M. Roberts, T. N. V. Karsili, B. Marchetti, D. Townsend &; V. G. Stavros, Solvent induced conformer specific photochemistry of guaiacol, Phys. Chem. Chem. Phys., 16, 16187, (2014). Interdisciplinary: Chemistry/Physics
Start Year 2012
 
Description Bristol Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited research talk at University of Bristol (April 2017)
Year(s) Of Engagement Activity 2017
 
Description Copenhagen Talk 
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Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited Research talk at University of Copenhagen, Denmark
Year(s) Of Engagement Activity 2015
 
Description DESY Talk 
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Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited research talk at the Centre for Free-Electron Laser Science (part of DESY) in Hamburg, Germany. Visit also provide time for extended and extremely useful discussions with many leading researchers working in related fields
Year(s) Of Engagement Activity 2017
 
Description Edinburgh Talk 
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Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited research talk at University of Edinburgh
Year(s) Of Engagement Activity 2015
 
Description IoP Workshop 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited research talk at IoP Molecular Physics Workshop, Caen, France 2015
Year(s) Of Engagement Activity 2015
URL http://www.open.ac.uk/science/physical-science-conferences/mol-phys-july-15
 
Description Leicester talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited departmental seminar at University of Leicester, November 2019
Year(s) Of Engagement Activity 2019
 
Description New Horizons in Chemical Physics talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at New Horizons in Chemical Physics meeting, held Oxford, April 2019
Year(s) Of Engagement Activity 2019
 
Description Open University Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
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Primary Audience Postgraduate students
Results and Impact Invited research talk at the Open University (October 2017)
Year(s) Of Engagement Activity 2017
 
Description Ultrafast Scotland Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Invited speaker talk at inaugural "Ultrafast Scotland" regional meeting (held 19th March 2018)
Year(s) Of Engagement Activity 2018
 
Description Warwick Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited research talk at University of Warwick (April 2016)
Year(s) Of Engagement Activity 2016
 
Description XLIC Conference presentaiton 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited research talk at 2nd COST XLIC Working Group 3 Meeting - Control of Chemical Reactivity in Belfast (April 2016). Three day meeting also provided plenty of time for extended discussion with many leading researchers in related fields.
Year(s) Of Engagement Activity 2016
 
Description York Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Invited talk at Department of Chemistry, University of York (21st November 2018)
Year(s) Of Engagement Activity 2018