Final Report Summary - ASTEX (Attosecond Science by Transmission and Emission of X-rays)
The project set out to develop new measurement technology that enabled the fastest events in nature to be resolved. This objective requires the use of methods that can achieve a sub-femtosecond (i.e. attosecond) time resolution (where 1 femtosecond is one millionth of a billionth of a second) which is the timescale needed to capture the full range of electron dynamics in matter. Further it was an objective that the methods be suitable even for solid materials and for this reason approaches that involved the use of emission and transmission of X-rays were therefore chosen i.e. hence the title "Attosecond Science by Transmission or Emission of X-rays" or ASTEX. This provides tools to measure diverse phenomena such as the full reaction dynamics in chemistry, the details of the process of photosynthesis and of the operation of solar cells. From this knowledge we can hope to engineer better processes and devices with benefit to greener energy and less resource demanding chemical synthesis.
The first achievement was in high harmonic generation (HHG) for imaging hole excitations created by strong field ionization and the study of their attosecond dynamics in polyatomic molecules. HHG spectroscopy in substituted benzenes was studied via new experimental and analysis techniques. In particular we have learnt how to unravel the dynamic contribution even for a polyatomic molecule that is not aligned. I also worked on the theory of selective imaging of hole dynamics induced by the removal of e.g. inner-valence electrons using the XUV initiated HHG technique. This resulted in the development not only of a theory of XiHHG, but also was key to developing a new experimental methodology (Auger spectroscopy) using X-ray FELs.
The next objective was to use X-ray transmission to realise attosecond pump-absorption probe spectroscopy. This resulted in optimised sources for VUV/XUV pump-probe spectroscopy with two colour sources synchronized to a few 10's attoseconds. Further I demonstrated for the first time isolated attosecond pulses from 150 eV - 600 eV with sufficient flux for time-resolved X-ray absorption measurements. Some of these capabilities were used first for attosecond X-ray absorption pump-probe techniques for gas phase systems. To this end I designed, built and commissioned an attosecond pump probe beamline for these measurements and conducted attosecond transient absorption measurements on laser dressed atoms with better than ~150 attosecond temporal resolution.
Finally the ambition of developing attosecond measurements for condensed phase materials (including liquids) have been advanced. We have carried out X-ray absorption spectroscopy of polymers at S L, C K and O K edges using our isolated attosecond pulses. A first time-resolved experiment in this challenging area is currently underway. In parallel I developed new techniques for measuring attosecond dynamics at surfaces and measured photoelectron wavepackets from surfaces using streaking method. developed liquid phase time-resolved photoelectron spectroscopy and liquid sheet jets of ~ 1 micron thickness for time-resolved X-ray absorption spectroscopy.
The research has thus led to new light sources and targets that will enable measurements of the very fastest electronic processes - unfolding on timescales of less than 1 fs - in gas phase molecules, and solid systems such as polymer films and liquids. New research is planned that builds on these techniques and applies them to the quantum control of dynamics in condensed phase systems.
The first achievement was in high harmonic generation (HHG) for imaging hole excitations created by strong field ionization and the study of their attosecond dynamics in polyatomic molecules. HHG spectroscopy in substituted benzenes was studied via new experimental and analysis techniques. In particular we have learnt how to unravel the dynamic contribution even for a polyatomic molecule that is not aligned. I also worked on the theory of selective imaging of hole dynamics induced by the removal of e.g. inner-valence electrons using the XUV initiated HHG technique. This resulted in the development not only of a theory of XiHHG, but also was key to developing a new experimental methodology (Auger spectroscopy) using X-ray FELs.
The next objective was to use X-ray transmission to realise attosecond pump-absorption probe spectroscopy. This resulted in optimised sources for VUV/XUV pump-probe spectroscopy with two colour sources synchronized to a few 10's attoseconds. Further I demonstrated for the first time isolated attosecond pulses from 150 eV - 600 eV with sufficient flux for time-resolved X-ray absorption measurements. Some of these capabilities were used first for attosecond X-ray absorption pump-probe techniques for gas phase systems. To this end I designed, built and commissioned an attosecond pump probe beamline for these measurements and conducted attosecond transient absorption measurements on laser dressed atoms with better than ~150 attosecond temporal resolution.
Finally the ambition of developing attosecond measurements for condensed phase materials (including liquids) have been advanced. We have carried out X-ray absorption spectroscopy of polymers at S L, C K and O K edges using our isolated attosecond pulses. A first time-resolved experiment in this challenging area is currently underway. In parallel I developed new techniques for measuring attosecond dynamics at surfaces and measured photoelectron wavepackets from surfaces using streaking method. developed liquid phase time-resolved photoelectron spectroscopy and liquid sheet jets of ~ 1 micron thickness for time-resolved X-ray absorption spectroscopy.
The research has thus led to new light sources and targets that will enable measurements of the very fastest electronic processes - unfolding on timescales of less than 1 fs - in gas phase molecules, and solid systems such as polymer films and liquids. New research is planned that builds on these techniques and applies them to the quantum control of dynamics in condensed phase systems.