Clumped hydrogen anomalies at cryogenic temperatures
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Molecular hydrogen is considered an indirect greehouse gas. In normal isotopic analysis, only the more abundant molecule of HD is considered, and the clumped isotopologue D2 is neglected, due to the low mixing ratio. Clumped isotopes are important when considering geological processes, or processes at or near thermodynamic equilibrium. In this work I determine the clumping anomaly of molecular hydrogen in the cryogenic region, with gases near atmospheric abundance ratios. Experiments were conducted between the -196°C and +350°C range, with a focus between -196°C and -78°C. Clumping anomaly for this focus range is between +1000 and +385 ‰, and experiments had a typical precision in range of 2-5‰. The low temperature experiments in this range underestimated the clumping anomaly, compared to theoretical predictions. The clumping anomalies have been determined to be independent of bulk isotopic composition of the gas, and independent of the previous clumping state of the gas. It is only a property of the equilibrium temperature of the gas. A change of temperature may partially explain the deviation from theoretical prediction, but this is not consistent over the experiment set. Conducted experiments have been verified by creating gases with known clumping anomaly. These experiments agreed with predictions.