0000000000184385
AUTHOR
Christoph Diehl
Isobar suppression in AMS using laser photodetachment
Abstract We are investigating the possibility of using laser photodetachment of negative atomic and molecular ions as an additional isobaric selection filter in accelerator mass spectrometry. The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at AMS facilities. We will focus on the astrophysical relevant radionuclide 182Hf, which is one of the isotopes measured with the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator) at the University of Vienna. Laser-induced isobar suppression is also of importance for radioactive-beam facilities. The present detection limit for measuring the isotope ratio 182Hf…
The electron affinity of phosphorus
We have measured the energies of all three fine structure components in the 3PJ ground state of the negative ion of phosphorus using laser photodetachment threshold spectroscopy. The experiment yielded an electron affinity of 746.68(6) meV. The ΔJ = 2–0, 2–1 and 1–0 fine structure splittings were determined to be 32.73(7) meV, 22.48(7) meV and 10.25(3) meV, respectively. In the experiment, a mass selected beam of P− ions was merged with the output from a pulsed infrared optical parametric oscillator. The residual atoms produced in the photodetachment process were detected and used as a monitor of the photon-energy dependence of the relative cross section. The Wigner law was fitted to each o…
Feasibility of photodetachment isobar suppression of WF with respect to HfF
Abstract The feasibility of using laser photodetachment as a means for isobar suppression in accelerator mass spectrometry has been investigated for the special case of HfF 5 − /WF 5 − . A method for absolute photodetachment cross section measurements was applied and the cross sections of tungsten pentafluoride and hafnium pentafluoride negative ions were measured. The measurements indicate that the photodetachment cross section for WF 5 − is at least 100 times larger than for HfF 5 − at the wavelength of the fourth harmonic of the Nd:YAG laser at 266 nm. The absolute cross section for WF 5 − at this photon energy was found to be (2.8 ± 0.3) × 10 −18 cm 2 , while an upper limit of 2 × 10 −…
Experimental investigation of electron impact onSi2−
A merged beams technique has been used to investigate collisions between electrons and $\text{Si}_{2}{}^{\ensuremath{-}}$ ions over a relative kinetic energy range of 0--210 eV. Absolute cross sections for pure electron detachment, detachment plus dissociation, and dissociation involving atomic and ionic products were measured. The dominant process over the energy range studied is pure electron detachment. A search for a resonance associated with a ${\text{Si}}_{2}$ dianion was made but none was observed.