title: A tabletop femtosecond time-resolved soft x-ray transient absorption spectrometer.
abstract: A laser-based, tabletop instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a homebuilt soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray charge coupled device camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterizations of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.
authors.affiliation: Departments of Chemistry and Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Zhi-Heng
authors.initials: ZH
authors.lastname: Loh
authors.forename: Munira
authors.initials: M
authors.lastname: Khalil
authors.forename: Raoul E
authors.initials: RE
authors.lastname: Correa
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Leone