We have developed an apparatus for performing laser-pump/$x$-ray-probe experiments in a COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) geometry. A soft $x$-ray beam is produced by focusing an intense (2$^{.}$10$^{14}$ W/cm$^{2 }$-- 2$^{.}$10$^{15}$ W/cm$^{2})$ and fast (6 fs -- 50 fs) laser beam into a thick (5 Torr -- 80 Torr) gaseous medium using three different techniques: an effusive jet, a gas cell and a hollow fiber. This beam is crossed with a room-temperature effusive (10$^{-3}$ Torr) gaseous target of Ar or Ne. The $x$-ray beam is analyzed in terms of its flux, harmonic energies and angular divergence by measuring full three dimensional photoelectron momentum images in coincidence with the recoil-ions. This apparatus will be used to perform time-dependent interferometry of dissociating H$_{2}^{+}$ (D$_{2}^{+})$ ions. Neutral H$_{2}$ (D$_{2})$ will be ionized and excited using an infrared pump pulse and probed after a time delay up to 240 fs with the soft x-ray pulses. The $x$-rays will be focused onto the target, and delayed relative to the pump pulse, using a two-component coaxial coated mirror to select a photon energy band in the 36-48 eV range. Preliminary results will be presented. *This work was supported by Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy.
This work was supported by the
Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences,
Office of Science, U.S. Department of Energy.
Submitted to DAMOP, May 2006 in Knoxville, TN.
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