New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1mbar

Abstract

In an effort to extend the pressure range for electron-based spectroscopies from ultrahigh vacuum into the so-called pressure gap region, we have built a new apparatus for in situ x-ray photoelectron spectroscopy up to 1mbar. The principle of the experimental setup is based on a modified hemispherical electron energy analyzer, a modified twin anode x-ray source, and several differential-pumping stages between sample region and electron detection. The reaction gas is provided in situ either by background dosing or, as a new feature, by beam dosing, using a directed gas beam from a small tube. The latter allows for higher local pressures. The performance of the new setup is discussed, deriving normalization procedures from the analysis of the attenuation of the substrate photoemission intensity by the increasing gas phase pressure. In addition, the change of the work function due to changes in surface composition can be evaluated in situ by analyzing the binding energy shift of the gas phase core-level peaks. As a first study, measurements for the pressure dependence of CO adsorption on Pd(111) between 5×10−8 and 1mbar are presented.

A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces

“…This approach has been used, beginning with Hans Siegbahn and coworkers early designs in the 1970's 10,11,12 , in all ambient pressure XPS instruments that have been designed to date. 13,14,15,16,17,18,19,20,21 A similar approach has been taken in the application of meta-stable impact electron spectroscopy (MIES) 22,23 for the study of surfaces, including liquids, at elevated pressures. 24 In addition to the scattering of electrons by gas molecules, there are other obstacles to overcome in ambient pressure XPS instruments, namely that the X-ray source (synchrotron or anode) and the electron analyzer have to be kept under UHV.…”

Steam reforming of methanol on PdZn near-surface alloys on Pd(1 1 1) and Pd foil studied by in-situ XPS, LEIS and PM-IRAS

“…From this study it appears likely that also water activation and the oxidation processes leading to CO 2 involve reactions at the bimetal-oxide phase boundary. On PdZn, in the absence of water, the formation of CO and H 2 both from formaldehyde and methanol [25] is a matter of fact, but Rösch and coworkers rather attributed this process to structural defects present on the 1:1 PdZn system [16].…”

Angle-resolved environmental X-ray photoelectron spectroscopy: A new laboratory setup for photoemission studies at pressures up to 0.4 Torr

“…[12][13][14] This paper presents the development and demonstrates the capabilities of a laboratory-based environmental XPS system incorporating an electrostatic lens system, which is able to acquire spectra up to 0.4 Torr. The incorporation of a two-dimensional (2D) detector provides imaging capabilities and allows the acquisition of angleresolved data in parallel mode over an angular range of 14 • .…”