Physics:Quantum atoms/spin isomers of hydrogen: Difference between revisions

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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''' 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>
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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.
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== References ==
== References ==
{{reflist|3}}
{{reflist|3}}
* {{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}}
* {{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}}
* {{Cite journal |last=Chen |first=Judy Y.-C. |last2=Li |first2=Yongjun |last3=Frunzi |first3=Michael |last4=Lei |first4=Xuegong |last5=Murata |first5=Yasujiro |last6=Lawler |first6=Ronald G. |last7=Turro |first7=Nicholas J. |title=Nuclear spin isomers of guest molecules in H2@C60, H2O@C60 and other endofullerenes |journal=Philosophical Transactions of the Royal Society A |year=2013 |volume=371 |issue=1998 |doi=10.1098/rsta.2011.0628 |pmid=23918710}}
* {{Cite journal |last=Matsumoto |first=Mitsuru |last2=Espenson |first2=James H. |title=Kinetics of the Interconversion of Parahydrogen and Orthohydrogen Catalyzed by Paramagnetic Complex Ions |journal=Journal of the American Chemical Society |year=2005 |volume=127 |issue=32 |pages=11447-11453 |doi=10.1021/ja0524292 |pmid=16089474}}


{{Author|Harold Foppele}}
{{Author|Harold Foppele}}

Revision as of 22:15, 23 May 2026

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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 H2. The two main forms are orthohydrogen and parahydrogen.[1]

Ortho and para hydrogen

In orthohydrogen, the two proton spins are parallel and the total nuclear spin is I=1. In parahydrogen, the two proton spins are antiparallel and the total nuclear spin is I=0.

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

  1. ↑ Atkins, Peter; de Paula, Julio (2006). Atkins' Physical Chemistry (8th ed.). W. H. Freeman. pp. 451-452. ISBN 0-7167-8759-8. 
  2. ↑ 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. 


Author: Harold Foppele


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