Abstract
Sub-μm thin samples are essential for spectroscopic purposes. The development of flat micro-jets enabled novel spectroscopic and scattering methods for investigating molecular systems in the liquid phase. However, the temperature of these ultra-thin liquid sheets in vacuum has not been systematically investigated. Here, we present a comprehensive temperature characterization using optical Raman spectroscopy of sub-micron flatjets produced by two different methods: colliding of two cylindrical jets and a cylindrical jet compressed by a high pressure gas. Our results reveal the dependence of the cooling rate on the material properties and the source characteristics, i.e., nozzle-orifice size, flow rate, and pressure. We show that materials with higher vapor pressures exhibit faster cooling rates, which is illustrated by comparing the temperature profiles of water and ethanol flatjets. In a sub-μm liquid sheet, the temperature of the water sample reaches around 268 K and the ethanol around 253 K close to the flatjet's terminus.
Highlights
X-ray absorption spectroscopy (XAS) is a powerful method for the investigation of fundamental electronic properties of matter
We present a comprehensive temperature characterization using optical Raman spectroscopy of sub-micron flatjets produced by two different methods: colliding of two cylindrical jets and a cylindrical jet compressed by a high pressure gas
Our results reveal the dependence of the cooling rate on the material properties and the source characteristics, i.e., nozzle-orifice size, flow rate, and pressure
Summary
X-ray absorption spectroscopy (XAS) is a powerful method for the investigation of fundamental electronic properties of matter. The use of XAS in the soft x rays is experimentally challenging in bulk materials, as transmission limits the sample thickness to some hundreds of nanometers.[1]. This is especially an experimental challenge for liquids to provide stable homogeneous thin samples in vacuum environment. Ultrathin liquid samples are very valuable for other techniques like ultrafast MeV electron diffraction, which has the advantage of shorter wavelength and stronger interaction with matter than x-rays.[4,5]. For MeV electron diffraction experiments in liquids, ultra-thin homogeneous samples are required to minimize noise contributions from inelastic electron-scattering events. The small penetration depths of highly energetic electrons are
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