We present a time-domain impulsive vibrational spectroscopy (IVS) setup capable of recording background- and baseline-free Raman spectra of excited electronic states in condensed-phase molecular systems. The setup records vibrational Raman spectra from 50-3000 cm-1 and is readily extended to follow spectral evolutions with a time resolution of < 20 fs, opening up the possibility for multi-dimensional Raman spectroscopy. Based on the setup, we explore a wide range of photochemical reactions aimed at gaining fundamental insights in the chemistry of excited electronic states. In rhodopsin, we investigate the consequences of vibrational wavepacket motion through a conical intersection. We identify the C11-H hydrogen out-of-plane mode as a coupling mode and devise a general model of how vibrational coherences can be used to obtain otherwise inaccessible structural information. In a second experiment, we determine the photoproduct distribution and dynamics upon isotopic substitution of selected hydrogen atoms along the retinal backbone. The results suggest a re-definition of the traditional Jablonski diagram for ultrafast photoreactions, which proceed faster than vibrational relaxation. In channelrhodopsin-1, we structurally characterise the primary photoproduct in the photocycle to be of 13-cis character. The study highlights the capabilities of IVS to obtain structural information for short-lived intermediate structures which are otherwise challenging to obtain. For the green fluorescent protein and all-trans retinal protonated Schiff base, we identify key excited-state (intermediate) structures and complement the studies with multi-dimensional Raman spectroscopy. The results provide a first picture of the structural origin of energy flow directly after photoexcitation. This thesis emphasises the capabilities of IVS beyond a proof-of-principle experiment and outlines the high potential of time-domain vibrational spectroscopy to reveal detailed structural information on ultrafast processes with high temporal resolution and sensitivity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:712433 |
| Date | January 2015 |
| Creators | Schnedermann, Christoph |
| Contributors | Kukura, Philipp |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:0fbfdfe7-13e6-4118-bfc0-2bff5f61834a |
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