W. B. Westerveld

Photoemission Cross Sections for Atomic Transitions in the Extreme Ultraviolet due to Electron Collisions with Atoms and Molecules

This article reviews experimental photoemission cross sections in the extreme ultraviolet, for transitions in excited atoms and atomic ions formed in electron collisions with atoms and molecules. A survey of the available experimental data for each investigated target gas reveals severe inconsistencies between cross sections reported by different laboratories. As almost all reported cross sections are based on relative measurements, a detailed discussion is given of the methods used for normalization of the cross sections.

A new method for measuring the retardation of a photoelastic modulator using single photon counting techniques

We present a new method to measure in situ the amplitude of the retardation for a photoelastic modulator polarimeter using single photon counting techniques. The method allows the simultaneous measurement of linear and circular polarization of light without the need for a separate calibration procedure. Comparison with measurements made with a λ/4‐retarder polarimeter show excellent agreement, confirming the method used.

Determination of density matrices of H(n = 3) atoms formed in charge transfer between protons and helium atoms

Abstract Fast hydrogen atoms are formed in charge transfer reactions between incident protons (60 keV) and helium atoms. The formed excited hydrogen atoms are allowed to decay in the presence of externally applied electric fields which dramatically change the intensity and polarization of the emitted radiation. Balmer-alpha radiation emitted from a 7 mm long section of the proton beam is measured as a function of applied electric field strength using a precision polarimeter. Detailed analysis of the experiment in which the time evolution of the hydrogen atoms in the presence of external fields is calculated allows the extraction of the full, axially symmetric density matrix of the H(n = 3) atoms at the time of their production.