Abstract
RationaleMolecular hydrogen (H2) is an important gas for atmospheric chemistry, and an indirect greenhouse gas due to its reaction with OH. The isotopic composition of H2 (ÎŽD) has been used to investigate its atmospheric budget; here we add a new observable, the clumped isotopic signature ÎDD, to the tools that can be used to study the global cycle of H2.MethodsA method for determining ÎDD in H2 was developed using the highâresolution MAT 253âUltra isotope ratio mass spectrometer (Thermo Fisher). The HH, HD and DD abundances are quantified at medium resolution (M/ÎM â 6000), which is sufficient for HD+ and DD+ to be distinguished from H3 + and H2D+, respectively. The method involves sequential measurement of isotopologues, and DD is measured using an ion counter. For verification, catalytic ÎDD equilibration experiments were performed at temperatures of up to 850°C.ResultsThe typical precision obtained for ÎDD is 2â6â°, close to the theoretical counting statistics limit, and adequate for detecting the expected natural variations. Compatibility and mediumâterm reproducibility are consistent with the precision values. The method was validated using temperature equilibration experiments, which showed a dependence of ÎDD on temperature as expected form theoretical calculations.ConclusionsWe have established a method for determining ÎDD in H2 at natural isotopic abundances, with a precision that is adequate for observing the expected variations in atmospheric and other natural H2. This method opens the road to new research on the natural H2 cycle.
Highlights
BACKGROUND AND INTRODUCTIONMolecular hydrogen (H2) is an important component of the terrestrial system, present in the atmospheric, oceanic, geologic, and biologic components
We have established a method for determining ÎDD in H2 at natural isotopic abundances, with a precision that is adequate for observing the expected variations in atmospheric and other natural H2
In this paper we report the first highâprecision (â° level) measurements of the abundance of DD in H2 at natural isotopic composition, using the new highâresolution, highâsensitivity MAT 253âUltra isotope ratio mass spectrometry (IRMS)
Summary
The typical precision obtained for ÎDD is 2â6â°, close to the theoretical counting statistics limit, and adequate for detecting the expected natural variations. Compatibility and mediumâterm reproducibility are consistent with the precision values. The method was validated using temperature equilibration experiments, which showed a dependence of ÎDD on temperature as expected form theoretical calculations
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have