Speaker
Description
Accelerator mass spectrometry (AMS) is commonly the most sensitive technique for detection of long-lived isotopes and has allowed identification of $^{60}$Fe and $^{244}$Pu signals in terrestrial and lunar archives from recent nearby nucleosynthesis.
Belonging to the middle-mass region of r-process nuclides, $^{182}$Hf (T$_{1/2}$=8.9$\,$Ma) could potentially be produced in different scenarios to those for $^{244}$Pu. However, AMS detection of astrophysical $^{182}$Hf has failed up to now due to the strong interference from its ubiquitous stable isobar $^{182}$W. Based on various yield- and elemental-ratio-calculations for possible $^{182}$Hf production scenarios, the estimated $^{182}$Hf/Hf signal intensity is at most a few times 10$^{−13}$, about two orders of magnitude below classical AMS sensitivity limits.
The novel Ion-Laser InterAction Mass Spectrometry (ILIAMS) technique achieves near-complete suppression of isobars via selective laser photodetachment and chemical reactions of decelerated anion beams in a gas-filled radio frequency quadrupole. It enables suppression of $^{182}$WF$_5$$^−$ vs. $^{182}$HfF$_5$$^−$ by >10$^5$ resulting in a W-corrected blank value of $^{182}$Hf/$^{180}$Hf=(3.4$\pm$2.1)$\times$10$^{–14}$.
We will highlight the potential of ILIAMS for sensitive detection of previously inaccessible long-lived radioisotopes and discuss ways to proceed in order to detect $^{182}$Hf at astrophysical levels including the challenges this poses in chemical sample preparation of HfF$_4$ from 100$\,$gram-amounts of deep-sea archives.
