van der Meer, A.F.G.
(Lex van der Meer)

FRAOS04 Coherent Protein Dynamics Explored at FELIX
Robert Austin (PU, Princeton, New Jersey), Britta Redlich, Lex van der Meer (FOM Rijnhuizen, Nieuwegein), Aihua Xie (OKSU-Phy, Stillwater - Oklahoma)

We have discovered that there exists a very narrow (less than 0.02 microns) wide resonance in the amide I band of myoglobin and photoactive yellow protein that can be driven to greater than 30% saturation using very narrow linewidth pump-probe spectroscopy at FELIX. The extraordinary narrowness of this transition and the extraordinary ease of saturation inplies that this band is highly anharmonic and decoupled from the other oscillators in the amide I band. We will present detailed measurments on this discovery and implications for energy flow in proteins.

TUAOS04 High Temporal Resolution, Single-Shot Electron Bunch-Length Measurements
Giel Berden, Britta Redlich, Lex van der Meer (FOM Rijnhuizen, Nieuwegein), Steven Jamison (Strathclyde University, Glasgow), Allan Gillespie, Allan MacLeod (UAD, Dundee)

A new technique, combining electro-optic detection of the Coulomb field of an electron bunch with single-shot cross-correlation of optical pulses is used to enable single-shot measurements of the electric field profile of sub-picosecond electron bunches. As in our previous "spectral decoding" technique (I. Wilke et al., Phys. Rev. Lett. 88(12) 2002), the electric field of the electron bunch is encoded electro-optically on an optical pulse. However, the new "temporal decoding" method offers a much better time resolution since it overcomes a fundamental time-resolution limit of the spectral decoding method, which arises from the inseparability of time and frequency properties of the probing optical pulse. The temporal decoding technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches.