1. Time-resolved gas electron diffraction – building a new apparatus in Edinburgh Derek A. Wann University of Edinburgh Workshop on Ultrafast Electron Sources UCLA 14 th December 2012

2. Acknowledgements Funding: Stuart Young Matthew Robinson Paul Lane

3. Overview Apparatus development Adapting the existing continuous source ED apparatus (not for this talk) Designing and building a time-resolved electron diffractometer What to study? Pump-probe studies of photoinduced dissociations / conformational changes / bond breaking or forming Future developments – including using MeV electrons in the UK My background My background in solving inorganic chemistry problems using time- averaged gas-phase ED data and quantum chemical methods

4. Electron diffraction in a previous life Performed ED studies of many novel and interesting inorganic species Range of sizes and complexities Understanding function using structures J. Phys. Chem. A, 2007, 111, 6103.Inorg. Chem., 2011, 50, 2988. Dalton Trans., 2008, 96. Inorg. Chem., 2012, 51, 3324. Electron gun Inlet system CCD camera

5. Current projects Awarded an EPSRC Career Acceleration Fellowship to do work with vibrationally cooled beams, and on time-resolved electron diffraction Two main areas of work developing the continuous beam apparatus building an entirely new apparatus in Edinburgh Chemistry’s Ti:sapphire laser lab Goals: understanding molecular structures and reaction dynamics based on direct diffraction measurements Computational chemistry is an important part of what we do can be very valuable in interpreting chemical phenomena

6. A 100 keV DC gun

7. Femtosecond laser used to produce electron beam and to pump molecules New time-resolved electron diffraction 100 keV electrons – pulsed up to kHz space-charge repulsion compact electron gun (simulated best resolution 500 fs) 100 kV electron gun chamber with vacuum pump Diffraction chamber with a magnetic lens, pulsed nozzle and vacuum pump Electron flight chamber with vacuum pump Detector chamber

8. Overall lab plan

9. Gases need nozzles Even-Lavie valve

10. Some possible studies In an excited electronic state C 60 has an enormous breathing mode causes increase in diameter of 30%! requires ~100 fs time resolution to observe Transition metal complexes known to undergo photoinduced isomerisations Helps if species of interest has some heavy atoms and undergoes a significant structural change upon excitation S–S C···C S–CS–C C–HC–H S···H S–CS–C C–HC–H S···C S···H Dissociations, such as H 3 CS-SCH 3 → H 3 CS·, would be very obvious

11. Relativistic electrons The EBTF at Daresbury has a 6 MeV electron gun Jim Clarke and colleagues keen to find uses for the apparatus Currently simulating the beam characteristics to see if electron diffraction can be possible

12. Conclusions Structure tells us a lot about function, but dynamics can tell us so much more Build on expertise to perform sub-ps gas-phase ED using a compact 100 keV DC electron gun 2013 should see the first electrons produced Working with central laboratory to investigate performing MeV diffraction