title: Development of high-repetition-rate laser pump/x-ray probe methodologies for synchrotron facilities.
abstract: We describe our implementation of a high repetition rate (54 kHz-6.5 MHz), high power (>10 W), laser system at the 7ID beamline at the Advanced Photon Source for laser pump/x-ray probe studies of optically driven molecular processes. Laser pulses at 1.06 μm wavelength and variable duration (10 or 130 ps) are synchronized to the storage ring rf signal to a precision of ~250 fs rms. Frequency doubling and tripling of the laser radiation using nonlinear optical techniques have been applied to generate 532 and 355 nm light. We demonstrate that by combining a microfocused x-ray probe with focused optical laser radiation the requisite fluence (with <10 μJ/pulse) for efficient optical excitation can be readily achieved with a compact and commercial laser system at megahertz repetition rates. We present results showing the time-evolution of near-edge x-ray spectra of a well-studied, laser-excited metalloporphyrin, Ni(II)-tetramesitylporphyrin. The use of high repetition rate, short pulse lasers as pump sources will dramatically enhance the duty cycle and efficiency in data acquisition and hence capabilities for laser-pump/x-ray probe studies of ultrafast structural dynamics at synchrotron sources.
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA. amarch@anl.gov
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: March
authors.forename: Andrew
authors.initials: A
authors.lastname: Stickrath
authors.forename: Gilles
authors.initials: G
authors.lastname: Doumy
authors.forename: Elliot P
authors.initials: EP
authors.lastname: Kanter
authors.forename: Bertold
authors.initials: B
authors.lastname: Krässig
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Southworth
authors.forename: Klaus
authors.initials: K
authors.lastname: Attenkofer
authors.forename: Charles A
authors.initials: CA
authors.lastname: Kurtz
authors.forename: Lin X
authors.initials: LX
authors.lastname: Chen
authors.forename: Linda
authors.initials: L
authors.lastname: Young