| 1. |
- Hinojosa, G., et al.
(författare)
-
Single photoionization of the Zn II ion in the photon energy range 17.5-90.0 eV: experiment and theory
- 2017
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 470:4, s. 4048-4060
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the single-photoionization cross-section of Cu-like Zn+ ions are reported in the energy (wavelength) range 17.5 eV (708 angstrom) to 90 eV (138 angstrom). The measurements on this trans-Fe element were performed at the Advanced Light Source synchrotron radiation facility in Berkeley, California at a photon energy resolution of 17 meV using the photon-ion merged-beams end-station. Below 30 eV, the spectrum is dominated by excitation autoionizing resonance states. The experimental results are compared with large-scale photoionization cross-section calculations performed using a Dirac Coulomb R-matrix approximation. Comparisons are made with previous experimental studies, resonance states are identified and contributions from metastable states of Zn+ are determined.
|
|
| 2. |
- Hinojosa, G., et al.
(författare)
-
Single photoionization of the Zn II ion in the photon energy range 17.5-90.0 eV: experiment and theory
- 2017
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 470:4, s. 4048-4060
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the single-photoionization cross-section of Cu-like Zn+ ions are reported in the energy (wavelength) range 17.5 eV (708 angstrom) to 90 eV (138 angstrom). The measurements on this trans-Fe element were performed at the Advanced Light Source synchrotron radiation facility in Berkeley, California at a photon energy resolution of 17 meV using the photon-ion merged-beams end-station. Below 30 eV, the spectrum is dominated by excitation autoionizing resonance states. The experimental results are compared with large-scale photoionization cross-section calculations performed using a Dirac Coulomb R-matrix approximation. Comparisons are made with previous experimental studies, resonance states are identified and contributions from metastable states of Zn+ are determined.
|
|
| 3. |
- Windelius, Olle, 1972, et al.
(författare)
-
A collinear angle-resolved photoelectron spectrometer
- 2017
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 410, s. 144-152
-
Tidskriftsartikel (refereegranskat)abstract
- In the present paper we describe a newly designed collinear photoelectron spectrometer for angular distribution measurements. We will henceforth refer to this instrument by the acronym PEARLS (PhotoElectron Angle-Resolved Linear Spectrometer). The design was motivated by the desire to collect electrons emitted from an extended linear source consisting of collinear photon and ion beams at a synchrotron radiation site. The electrons could be produced in either photoionization or photodetachment events. The primary advantage of a collinear beams geometry is that the effective interaction volume can be made much larger than that obtainable with a crossed beams geometry, which has been used in many earlier photoelectron spectroscopic studies. The present apparatus is capable of collecting electrons over a beam source length of 22 cm. The electrons are detected using Channel Electron Multipliers (CEMs). There are 4 detector planes placed perpendicular to the direction of the beam source, where each plane contains 4 CEMs. The use of all 4 detector planes with a total of 16 CEMs enhances the photoelectron signal, which is important at a synchrotron radiation site where the photon flux is typically low. If photoelectrons of different energies are emitted, the design allows for electrostatic energy analyzers to be placed in front of the CEMs. We have performed a photodetachment experiment to demonstrate the functionality of the PEARLS apparatus using a pulsed laser as the photon source. In particular, we have measured the angular distribution of photoelectrons ejected from Ag- at two different photon energies. © 2017 Elsevier B.V.
|
|
| 4. |
- Windelius, Olle, 1972
(författare)
-
A Collinear Angle-Resolved Photoelectron Spectrometer - Instrumental Design and Photodetachment Measurements
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For more than half a century, photoelectron spectroscopy has been used to investi- gate atoms, ions and molecules. Various techniques have been developed in order to measure electron energies and angular distributions using different radiation sources such as lasers and synchrotrons. In this work, a new spectrometer design for measurements of angular distributions of photoelectrons using synchrotron ra- diation is presented. The design takes advantage of a collinear interaction region, which is two orders of magnitude larger than obtainable with the crossed beams method. The number of events per time unit is thereby substantially increased compared to regular angle-resolved photoelectron spectrometers. This is of great value when the radiation source has a low photon flux and the background is large due to the high photon energy. The spectrometer has been tested on sys- tems where the angular distribution is well-known, in order to develop methods for compensation of the angular transformation between the ion rest frame and the lab frame. Further, a measurement of the angular distribution of a negative ion, P−, over a wide range of photon energies has been conducted. The results are in agreement with previous measurements and, more importantly, reveal new and valuable information about the theoretical modelling of angular distributions. The experiments presented show that the spectrometer can be used to measure angular distributions of atomic and molecular ions, and that it can be a valuable asset at synchrotron beamline endstations. This work also includes a photoion- ization cross section measurement of Zn+, performed using the synchrotron at the Advanced Light Source (ALS), Berkeley, CA.
|
|
| 5. |
- Windelius, Olle, 1972, et al.
(författare)
-
Photoelectron angular distributions in photodetachment from P
- 2021
-
Ingår i: Physical Review A. - 2469-9926 .- 2469-9934. ; 103:3
-
Tidskriftsartikel (refereegranskat)abstract
- The angular distributions of electrons ejected in laser photodetachment of the P- ion have been studied in the photon energy range of 0.95-3.28 eV using a photoelectron spectrometer designed to accommodate a source consisting of collinearly overlapping photon and negative ion beams. We observe the value of the asymmetry parameter beta starting at zero near the threshold, falling to almost -1 about 0.5 eV above the threshold and eventually rising to a positive value. The experimental data has been fitted to a simplified model of the Cooper-Zare formula which yields a qualitative understanding of the quantum interference between the outgoing s and d waves representing the free electron. The present results are also compared with previous results for other elements involving p-electron photodetachment.
|
|
