(a) The liquid microjet endstation installed at the SIM beamline of the Swiss Light Source. (b) The Scienta HiPP-2 R4000 electron spectrometer has six lens elements, three in the pre-lens and three in the (traditional) lens. (c) The incoming photon beam, the liquid microjet direction of flow, and the electron analyzer detection axis are orthogonal with one another.
(a) The liquid microjet and all of its components are mounted to the bottom DN-200 flange. (b) The mu-metal liner is designed to allow simple access to the measurement area. The overall magnetic field inside the liner with the liquid microjet installed is less than 15 μT.
The liquid microjet travels 1.5 cm inside the measurement chamber before it enters a 600 μm catcher and is directly drained outside the vacuum chamber where it can be recycled for further study. The diameter of the liquid microjet filament is variable, but typically in the 20–40 μm size range. The liquid filament depicted has been artificially enhanced for clarity.
Potentials applied to the six electrostatic lens elements of the Scienta HiPP-2 R4000 electron spectrometer for 10 eV pass energy as a function of electron kinetic energy over the range of 2–60 eV. An accelerating potential is applied to the L1p element (see Figure 1(b) ). At electron kinetic energies above 60 eV L1p is grounded and a traditional lens mode is employed.
Entrance cones of the Scienta HiPP-2 R4000 electron spectrometer used with the liquid microjet. The truncated cone exposes the L1p element to the measurement zone and allows for an accelerating field to be applied to photoelectrons below 60 eV. The working distance of the truncated cone is 9 mm. The traditional cone is used in liquid microjet studies at ambient pressure conditions up to 20 mbar and has an aperture diameter typically between 0.1 and 0.8 mm. The working distance of the traditional cone is on the order of the aperture diameter.
A plug is used to seal off the electron analyzer vacuum system from the liquid microjet ionization chamber during venting and allows for quick venting of only the liquid microjet chamber. This manner of sealing off the analyzer works well and can maintain a vacuum of 1 × 10−8 mbar at the detector with the main analysis chamber vented to ambient air.
A schematic representation of the vacuum system of the Scienta HiPP-2 R4000 energy analyzer and the liquid microjet chamber. The pressures shown were recorded during operation of the liquid microjet with the truncated entrance cone.
Nitrogen 1s photoelectron spectra collected at (a) 35 eV and (b) 995 eV electron kinetic energy from a 0.25 M aqueous solution of butylamine. (a) Collected using the accelerating lens table presented in Sec. II B and shown in Figure 4 . (b) Collected using a traditional lens table that grounds the L1p element. Both spectra were recorded using the truncated entrance cone. Each spectrum is fit using two Gaussian functions following standard background subtraction. The component at low kinetic energy is assigned to protonated butylamine (shown in red) whereas the component at high kinetic energy arises from neutral butylamine (shown in blue).
The ratio of the integrated area of the R-NH3 + to R-NH2 components of the nitrogen 1s photoelectron spectra from a 0.25 M aqueous solution of butylamine at pH 10.2 as a function of electron kinetic energy. The curve parallels the shape of the universal inelastic mean free path curve of solids. 25 A distinct minimum is evident between 60 and 100 eV. This energy window affords the most sensitivity to the vapor-water interface. At energies on both sides of the minimum the probe depth of the experiment increases.
Ultraviolet photoemission spectra recorded using He II α excitation at 40.8 eV from a liquid microjet of 0.05 M NaCl. The top spectrum is recorded with the liquid microjet in the focal plane of the electron analyzer and consists of both liquid and gas phase water. The gas phase spectrum is recorded by displacing the liquid microjet filament 500 μm away from the electron analyzer focus and out of the incident photon path. The difference spectrum provides the signature of liquid water. 13
(solid line) Normalized silicon fluorescence yield K-edge X-ray absorption spectrum from aqueous 3 wt.% colloidal SiO2 Ludox SM collected with the liquid microjet installed in the permanent endstation of the Phoenix beamline. 24 (red squares) Partial electron yield XAS data collected using the new endstation from a liquid microjet of 10 wt.% Ludox CL at 1820, 1848, and 1876 eV.
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