Abstract
We demonstrate the applicability of third- and fifth-order harmonics of free-electron laser (FEL) radiation for soft X-ray absorption spectroscopy in the transmission mode at SACLA BL1, which covers a photon energy range of 20 to 150 eV in the fundamental FEL radiation. By using the third- and fifth-order harmonics of the FEL radiation, we successfully recorded near-edge X-ray absorption fine structure (NEXAFS) spectra for Ar 2p core ionization and CO2 C 1s and O 1s core ionizations. Our results show that the utilization of third- and fifth-order harmonics can significantly extend the available photon energies for NEXAFS spectroscopy using an FEL and opens the door to femtosecond pump-probe NEXAFS using a soft X-ray FEL.
Highlights
Free-electron lasers (FELs) [1] provide a source of intense, coherent, ultrafast, and continuously tunable radiation
We propose and demonstrate the utilization of third- and fifth-order harmonics in FEL radiation to extend the available photon energy region
While the highest available photon energy is 150 eV in the fundamental FEL radiation at SACLA BL1, we demonstrate soft X-ray absorption spectroscopy at the Ar 2p and CO2 C 1s and O 1s edges, successfully recording near-edge X-ray absorption fine structure (NEXAFS) spectra by using the third- and fifth-order harmonics in the FEL radiation
Summary
Free-electron lasers (FELs) [1] provide a source of intense, coherent, ultrafast, and continuously tunable radiation. Since the development of the self-amplified spontaneous-emission (SASE) technique [2,3], which extended the available laser wavelengths to the X-ray regime [4,5,6,7,8], great interest has been shown by user communities over a wide range of fields in physics [9,10], chemistry [11,12], and structural biology [13,14]. X-ray FELs have made it possible to observe structural changes which occur at femtosecond timescales. X-ray diffraction image of three Au(CN)2 − molecules in solution using a 267 nm wavelength pump and X-ray FEL probe [15,16]. Techniques using diffraction mainly require X-rays of energy. It is difficult to apply this method to biological molecules, which consist mainly of light elements such as carbon, nitrogen, and oxygen, and do not contain heavy elements
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