Abstract
We present a proof of principle experiment on single-shot near edge soft X-ray fine structure (NEXAFS) spectroscopy with the use of a laboratory laser-plasma light source. The source is based on a plasma created as a result of the interaction of a nanosecond laser pulse with a double stream gas puff target. The laser-plasma source was optimized for efficient soft X-ray (SXR) emission from the krypton/helium target in the wavelength range from 2 nm to 5 nm. This emission was used to acquire simultaneously emission and absorption spectra of soft X-ray light from the source and from the investigated sample using a grazing incidence grating spectrometer. NEXAFS measurements in a transmission mode revealed the spectral features near the carbon K-α absorption edge of thin polyethylene terephthalate (PET) film and L-ascorbic acid in a single-shot. From these features, the composition of the PET sample was successfully obtained. The NEXAFS spectrum of the L-ascorbic acid obtained in a single-shot exposure was also compared to the spectrum obtained a multi-shot exposure and to numerical simulations showing good agreement. In the paper, the detailed information about the source, the spectroscopy system, the absorption spectra measurements and the results of the studies are presented and discussed.
Highlights
X-ray absorption fine structure (XAFS) spectroscopy allows for the chemical environment of the sample to be investigated by studying X-ray absorption of the sample in the vicinity and above the core level binding energy of the considered atom
Typical optical density OD near edge soft X-ray fine structure (NEXAFS) spectra for polyethylene terephthalate (PET) foil obtained with this system are depicted in Figure 4, for various laser energies ranging from
soft X-ray (SXR) pulse NEXAFS spectrum was obtained using 300 SXR pulses emitted from the Kr/He plasma multiple SXR pulse NEXAFS spectrum was obtained using 300 SXR pulses emitted from the Kr/He generated by the interaction of 0.6 J energy and 3 ns duration Nd:YAG laser pulses
Summary
X-ray absorption fine structure (XAFS) spectroscopy allows for the chemical environment of the sample to be investigated by studying X-ray absorption of the sample in the vicinity and above the core level binding energy of the considered atom. Such plasma emits radiation in the broad range of wavelengths, from soft X-rays to infrared, depending on the gas used as a target, laser beam and focusing system parameters In this experiment, an efficient soft X-ray emission from krypton was achieved (as depicted in the inset of Figure 1, for E = 6.7 J laser pulse with 1.3 ns time duration) and employed for a single SXR pulse NEXAFS spectroscopy. For the efficient emission in the SXR region used in the NEXAFS experiment, especially to be able to record high signal to noise ratio reference and sample spectra in a single SXR pulse, the krypton/helium target laser plasma source was properly optimized. ~10%, according to the CXRO data [28]
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