Wieman Scott T.

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Last Name
Wieman
First Name
Scott T.
ORCID
0000-0002-6415-5293

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  • Article
    Development of a quantum cascade laser absorption spectrometer for simultaneous measurement of 13C-18O and 18O-18O clumping in CO2
    (Wiley, 2024-06-18) Wieman, Scott T. ; Kapit, Jason ; Michel, Anna P. M. ; Guo, Weifu
    Dual clumped isotope paleothermometry determines carbonate formation temperatures by measuring the frequency of 13C–18O (∆638) and 18O–18O (∆828) pairs in carbonates. It resolves isotopic kinetic biases and thus enables more accurate paleotemperature reconstructions. However, high-precision measurements of 18O–18O clumping using current techniques requires large sample sizes and long acquisition times. We developed a mid-infrared isotope ratio laser spectrometer (IRLS) for simultaneous measurement of the isotopologue ratios ∆638 and ∆828 in gas-phase carbon dioxide (CO2) at room temperature. Our IRLS uses a single laser scanning from 2290.7 to 2291.1 cm−1 and a 31 m pathlength optical cell, and it simultaneously measures the five isotopologues required for calculating ∆638 and ∆828: 16O12C16O, 16O13C16O, 16O12C18O, 16O13C18O, and 18O12C18O. In addition, our IRLS can measure 16O12C17O, enabling ∆17O analysis. At ~20°C and a CO2 pressure of ~2 Torr, our IRLS system achieved precisions of 0.128‰ and 0.140‰ within 20 s for abundances of the clumped isotopologues 16O13C18O and 18O12C18O, respectively, and precisions of 0.267‰, 0.245‰, and 0.128‰ for 16O12C16O, 16O13C16O, and 16O12C18O. This yielded precisions of 0.348‰ (∆638) and 0.302‰ (∆828) within 25 s. Simulated sample–reference switching highlights the potential of our system and the need for further development. We demonstrated simultaneous measurements of ∆638 and ∆828 in CO2 to precisions of <0.35‰ within 25 s using a room-temperature, single-laser IRLS. Future developments on better resolving 16O12C16O and 16O13C16O peaks and system temperature control could further improve the measurement precision.
  • Dataset
    Voltage scans from a prototype hollow core fiber isotope ratio laser spectrometer
    (Woods Hole Oceanographic Institution, 2024-08-22) Wieman, Scott T. ; Kapit, Jason ; Guo, Weifu ; Michel, Anna P. M.
    This dataset consists of 900 one-second-long voltage acquisitions across 2000 detector channels from a prototype hollow core fiber isotope ratio laser spectrometer developed and operated at the Woods Hole Oceanographic Institution’s David Center for Ocean Innovation. Each acquisition covers a spectral range of ~2290.55 to 2299.15 cm-1. The operational conditions are 2.5 torr of pure CO2 in a 1m-long hollow core fiber with an inner diameter of 200 µm at room temperature (~20ºC). The laser was scanned across this spectral range at 50kHz and each one-second acquisition is the average of 50000 individual spectral scans within that one second.