Efficient table-top dual-wavelength beamline for ultrafast transient absorption spectroscopy in the soft X-ray region

Abstract

We present a table-top beamline providing a soft X-ray supercontinuum extending up to 350 eV from high-order harmonic generation with sub-13 fs 1300 nm driving pulses and simultaneous production of sub-5 fs pulses centered at 800 nm. Optimization of the high harmonic generation in a long and dense gas medium yields a photon flux of ~2 x 10 7 photons/s/1% bandwidth at 300 eV. The temporal resolution of X-ray transient absorption experiments with this beamline is measured to be 11 fs for 800 nm excitation. This dual-wavelength approach, combined with high flux and high spectral and temporal resolution soft X-ray absorption spectroscopy, is a new route to the study of ultrafast electronic dynamics in carbon-containing molecules and materials at the carbon K-edge. 2/10 Description of the table-top dual-wavelength beamlineThe beamline is summarized in Figure 1. It uses a 13 mJ , 800 nm, 30 fs, 1 kHz Ti:Sapphire laser (Coherent Legend Elite Duo), whose energy is split into 11 mJ +2 mJ to produce the probe and pump pulses, respectively, used in time-resolved X-ray transient absorption experiments. This section details the simultaneous compression of SWIR (centered at 1300 nm or 1400 nm) and visible-near infrared (centered at 800 nm) pulses, and the characteristics of the soft X-ray spectrometer. Production of few-cycle short-wave infrared pulsesThe few-cycle pulses centered at 1300 nm in the SWIR are produced using an OPA followed by spectral broadening in a hollow-core fiber filled with a rare gas 35 and compression with chirped mirrors 36 . The 11 mJ 800 nm beam is further split into 0.5 mJ and 10.5 mJ for use in a two-stage OPA, which converts the 800 nm to SWIR (1300 nm). The two-stage system is obtained from Light Conversion and is designed to provide CEP stability of the signal pulses. The first stage is a low energy OPA (TOPAS Prime), pumped by 0.5 mJ, which provides 90 J of 2 m pulses in the idler. Due to the parametric amplification process, the idler pulses are passively CEP stabilized, with a stability of <200 mrad. They are then used as the seed for the white light generation in a second, high energy, OPA (HE-TOPAS) pumped with the remaining 10.5 mJ of 800 nm light. This design should ensure the CEP stability of the signal pulses over the 1200-1600 nm tunable range of the OPA, regardless of the CEP stability of the pump laser. However, the following results are obtained with a CEP-averaged signal pulse. The 2.8 mJ, 1300 nm, 40 fs output is focused with a 2-m focusing mirror to a focal size of 390 m (at 1/e 2 ) at the entrance of a 3-m-long, 700-m-inner diameter stretched hollow-core fiber (HCF) filled with 0.4 bar of argon (Few-Cycle Inc.). The ratio of beam

Simulating X-ray photoelectron spectra with strong electron correlation using multireference algebraic diagrammatic construction theory

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Table-Top X-ray Spectroscopy of Benzene Radical Cation

“…The recent development of tabletop high-harmonic generation (HHG) sources reaching up to 300 eV photon energies in the x-ray 1,2,3,4,5,6,7,8,9,10 gives rise to a powerful pump-probe technique that combines near-infrared (NIR) or ultraviolet (UV) excitation and soft x-ray spectroscopic probing in the carbon K-edge region. Promotion of an electron from the carbon K-edge 1s orbitals to vacant or partially vacant valence orbitals following NIR/UV excitation or ionization provides the opportunity to follow ultrafast electronic structural changes via the x-ray spectroscopic regime.…”

Core level photoelectron spectroscopy of heterogeneous reactions at liquid–vapor interfaces: Current status, challenges, and prospects

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