Producing and quantifying enriched <i>para</i>-H2

Tom, Brian A.; Bhasker, Siddhartha; Miyamoto, Yuki; Momose, Takamasa; McCall, Benjamin J.

doi:10.1063/1.3072881

Cited by 67 publications

(57 citation statements)

References 22 publications

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“…The goal of the experiment is to measure the ortho : para ratio of H + 3 (rather, the p-H + 3 fraction p 3 ) in a hydrogenic plasma of known p-H 2 fraction (p 2 ) at a known temperature. Hydrogen gas with a known p-H 2 fraction was prepared by combining appropriate amounts of high-purity normal hydrogen and > 99.9 per cent pure p-H 2 (produced with a p-H 2 converter [19]) to give mixtures of 25, 40, 50, 66, 83 and > 99.9 per cent p-H 2 . This gas flowed into a hollow cathode plasma cell made from an approximately 4 m cylindrical copper tube encased in a glass cell evacuated with a mechanical pump.…”

Section: Methodsmentioning

confidence: 99%

The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas

Crabtree

McCall

2012

Phil. Trans. R. Soc. A.

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In diffuse molecular clouds, the nuclear spin temperature of H + 3 (approx. 30 K) is much lower than the cloud kinetic temperature (approx. 70 K). To understand this temperature discrepancy, we have measured the ratio of the hop to exchange pathways (a) in the H + 3 + H 2 → H 2 + H + 3 reaction (which interconverts ortho-and para-H + 3 ) using high-resolution spectroscopy of the n 2 fundamental band of H + 3 in a hydrogenic plasma. We find that a decreases from 1.6 ± 0.1 at 350 K to its statistical value of 0.5 ± 0.1 at 135 K. We use this result to model the steady-state chemistry of diffuse molecular clouds, finding good agreement with astronomical data provided the dissociative recombination rates of orthoand para-H

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Section: Methodsmentioning

confidence: 99%

The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas

Crabtree

McCall

2012

Phil. Trans. R. Soc. A.

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“…The crystal was grown with 99.98% pure para-H 2 [13] following the pressurized crystal-growth method [14], which is known to yield a transparent single crystal. Para-H 2 gas was condensed into the cell at 15-20 K, while the liquid level was watched.…”

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confidence: 99%

Refractive index measurements of solid parahydrogen

et al. 2011

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“…These properties can be used to measure the pH 2 enrichment in an unknown sample. 4,9,[21][22][23] Nevertheless, many of these measurements often require that other parameters also be measured very accurately (e.g. temperature and pressure), and require calibration with known mixtures to provide quantitative results.…”

Section: Introductionmentioning

confidence: 99%

“…temperature and pressure), and require calibration with known mixtures to provide quantitative results. 15,21,24 However, as the two spin isomers occupy different rotational energy levels, 1,3,4,25 it is possible to use Raman spectroscopy to probe the rotational transitions of H 2 gas, and hence determine the composition of pH 2 without calibration mixtures. 8,13,14,25,26 In the context of monitoring pH 2 enrichment, Sundararajan et al 10 used a Raman microscope with a 514 nm laser for off-line monitoring of H 2 gas used for matrix isolation spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Quantitative In Situ Monitoring of Parahydrogen Fraction Using Raman Spectroscopy

Parrott

Dallin²,

Andrews³

et al. 2018

Appl Spectrosc

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Raman spectroscopy has been used to provide a rapid, non-invasive and non-destructive quantification method for determining the parahydrogen fraction of hydrogen gas. The basis of the method is the measurement of the ratio of the first two rotational bands of hydrogen at 355 cm −1 and 586 cm −1 corresponding to parahydrogen and orthohydrogen, respectively. The method has been used to determine the parahydrogen content during a production process and a reaction. In the first example, the performance of an in-house liquid nitrogen cooled parahydrogen generator was monitored both at-line and on-line. The Raman measurements showed that it took several hours for the generator to reach steady state and hence, for maximum parahydrogen production (50 %) to be reached. The results obtained using Raman spectroscopy were compared to those obtained by at-line low-field NMR spectroscopy. While the results were in good agreement, Raman analysis has several advantages over NMR for this application. The Raman method does not require a reference sample, as both spin isomers (ortho and para) of hydrogen can be directly detected, which simplifies the procedure and eliminates some sources of error. In the second example, the method was used to monitor the fast conversion of parahydrogen to orthohydrogen in-situ. Here the ability to acquire Raman spectra every 30 s enabled a conversion process with a rate constant of 27.4 × 10 −4 s −1 to be monitored. The Raman method described here represents an improvement on previously reported work, in that it can be easily applied on-line and is approximately 500 times faster. This offers the potential of an industrially compatible method for determining parahydrogen content in applications that require the storage and usage of hydrogen.

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Producing and quantifying enriched para-H2

Cited by 67 publications

References 22 publications

The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas

The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas

Refractive index measurements of solid parahydrogen

Quantitative In Situ Monitoring of Parahydrogen Fraction Using Raman Spectroscopy

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Producing and quantifying enriched para-H2

Cited by 67 publications

References 22 publications

The ortho : para ratio of H 3 + in laboratory and astrophysical plasmas

The ortho : para ratio of H 3 + in laboratory and astrophysical plasmas

Refractive index measurements of solid parahydrogen

Quantitative In Situ Monitoring of Parahydrogen Fraction Using Raman Spectroscopy

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The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas

The ortho : para ratio of H ₃ ⁺ in laboratory and astrophysical plasmas