Physics:Quantum atoms/spin isomers of hydrogen: Difference between revisions
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{{Short description|Nuclear spin isomers of molecular hydrogen}} | |||
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'''Spin isomers of hydrogen''' are forms of molecular hydrogen that differ in the relative nuclear spin orientation of the two protons in <math>\mathrm{H}_2</math>. The two main forms are '''orthohydrogen''' and '''parahydrogen'''. | '''spin isomers of hydrogen''' is a Book II topic in the Quantum Collection. '''Spin isomers of hydrogen''' are forms of molecular hydrogen that differ in the relative nuclear spin orientation of the two protons in <math>\mathrm{H}_2</math>. The two main forms are '''orthohydrogen''' and '''parahydrogen'''.<ref>{{Cite book |last=Atkins |first=Peter |last2=de Paula |first2=Julio |title=Atkins' Physical Chemistry |edition=8th |publisher=W. H. Freeman |year=2006 |pages=451-452 |isbn=0-7167-8759-8}}</ref> The distinction is quantum mechanical because the nuclear spin wavefunction must combine with the rotational state to satisfy exchange symmetry. Ortho and para hydrogen have different allowed rotational levels, thermal populations, and low-temperature properties. Spin-isomer conversion matters in cryogenics, molecular spectroscopy, hydrogen storage, and precision studies of simple molecules. | ||
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[[File:Quantum_atoms_spin_isomers_of_hydrogen_concept_map.svg|thumb|280px|spin isomers of hydrogen in the Quantum Collection.]] | |||
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== Quantum significance == | == Quantum significance == | ||
The ortho and para forms have different rotational energy level populations and different low-temperature behavior. At room temperature hydrogen is mostly orthohydrogen, while at very low temperature the para form is energetically favored. | The ortho and para forms have different rotational energy level populations and different low-temperature behavior. At room temperature hydrogen is mostly orthohydrogen, while at very low temperature the para form is energetically favored.<ref>{{Cite journal |last=Matthews |first=M. J. |last2=Petitpas |first2=G. |last3=Aceves |first3=S. M. |title=A study of spin isomer conversion kinetics in supercritical fluid hydrogen for cryogenic fuel storage technologies |journal=Applied Physics Letters |year=2011 |volume=99 |issue=8 |page=081906 |doi=10.1063/1.3628453}}</ref> | ||
Spin isomers are important in cryogenics, molecular spectroscopy, nuclear spin physics, and precision studies of hydrogen molecules. | Spin isomers are important in cryogenics, molecular spectroscopy, nuclear spin physics, and precision studies of hydrogen molecules. | ||
== See also == | == See also == | ||
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}} | |||
== References == | == References == | ||
{{reflist|3}} | {{reflist|3}} | ||
{{Author|Harold Foppele}} | {{Author|Harold Foppele}} | ||
Latest revision as of 23:33, 23 May 2026
spin isomers of hydrogen is a Book II topic in the Quantum Collection. Spin isomers of hydrogen are forms of molecular hydrogen that differ in the relative nuclear spin orientation of the two protons in . The two main forms are orthohydrogen and parahydrogen.[1] The distinction is quantum mechanical because the nuclear spin wavefunction must combine with the rotational state to satisfy exchange symmetry. Ortho and para hydrogen have different allowed rotational levels, thermal populations, and low-temperature properties. Spin-isomer conversion matters in cryogenics, molecular spectroscopy, hydrogen storage, and precision studies of simple molecules.
Ortho and para hydrogen
In orthohydrogen, the two proton spins are parallel and the total nuclear spin is . In parahydrogen, the two proton spins are antiparallel and the total nuclear spin is .
Because protons are fermions, the total molecular wavefunction must have the proper exchange symmetry. This links the nuclear spin state to the allowed rotational states of the molecule.
Quantum significance
The ortho and para forms have different rotational energy level populations and different low-temperature behavior. At room temperature hydrogen is mostly orthohydrogen, while at very low temperature the para form is energetically favored.[2]
Spin isomers are important in cryogenics, molecular spectroscopy, nuclear spin physics, and precision studies of hydrogen molecules.
See also
Table of contents (84 articles)
Index
Full contents
References
- ↑ Atkins, Peter; de Paula, Julio (2006). Atkins' Physical Chemistry (8th ed.). W. H. Freeman. pp. 451-452. ISBN 0-7167-8759-8.
- ↑ Matthews, M. J.; Petitpas, G.; Aceves, S. M. (2011). "A study of spin isomer conversion kinetics in supercritical fluid hydrogen for cryogenic fuel storage technologies". Applied Physics Letters 99 (8): 081906. doi:10.1063/1.3628453.
