Grundlagen der Photochemie.

Bonhoeffer, K. F.; Harteck, P.

doi:10.1021/j150353a013

Cited by 26 publications

(36 citation statements)

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“…The rotational anomaly has been observed also in solid environment for various H containing molecules such as H 2 , CH 4 , H 2 O, NH 3 , CH 3 , CH 3 OH, and CH 3 F. [17][18][19][20][21][22][23][24][25][26][27] In condensed phases, the conversion process is accelerated by the existence of phonons. The acceleration of the nuclear spin conversion by phonons makes the conversion rates in a time scale of 1 -10 5 s in cryomatrices despite the weakness of the intrinsic magnetic interactions.…”

Section: Introductionmentioning

confidence: 87%

“…[2][3][4] In the absence of collisions and external magnetic field, different nuclear spin states of these molecules are expected to behave as distinct species similar to chemical isotopes and have been of great interest in physical chemistry [5][6][7][8][9][10] as well as in astrochemistry. A well-known case is the nuclear spin isomers of hydrogen molecules, H 2 .…”

Section: Introductionmentioning

confidence: 99%

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Nuclear spin conversion of methane in solid parahydrogen

Miyamoto

Fushitani

Ando

et al. 2008

The Journal of Chemical Physics

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The nuclear spin conversion of CH(4) and CD(4) isolated in solid parahydrogen was investigated by high resolution Fourier transform infrared spectroscopy. From the analysis of the temporal changes of rovibrational absorption spectra, the nuclear spin conversion rates associated with the rotational relaxation from the J=1 state to the J=0 state for both species were determined at temperatures between 1 and 6 K. The conversion rate of CD(4) was found to be 2-100 times faster than that of CH(4) in this temperature range. The faster conversion in CD(4) is attributed to the quadrupole interaction of D atoms in CD(4), while the conversion in CH(4) takes place mainly through the nuclear spin-nuclear spin interaction. The conversion rates depend on crystal temperature strongly above 3.5 K for CH(4) and above 2 K for CD(4), while the rates were almost constant below these temperatures. The temperature dependence indicates that the one-phonon process is dominant at low temperatures, while two-phonon processes become important at higher temperatures as a cause of the nuclear spin conversion.

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Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Nuclear spin conversion of methane in solid parahydrogen

Miyamoto

Fushitani

Ando

et al. 2008

The Journal of Chemical Physics

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“…There are several cases, however, where the nuclear hyperfine interaction is important. It is known that catalysts such as paramagnetic molecules, 7,8 ions, 9 or surfaces 10,11 accelerate the conversion between different nuclear spin symmetry species by producing strong inhomogeneity of the local magnetic field during a collision. 2 The conversion can also occur by quantum relaxation through the mixing of nearly degenerate molecular internal states of different nuclear spin symmetries.…”

Section: Introductionmentioning

confidence: 99%

Nuclear spin selection rules for reactive collision systems by the spin-modification probability method

Park

Light

2007

The Journal of Chemical Physics

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The spin-modification probability (SMP) method, which provides fundamental and detailed quantitative information on the nuclear spin selection rules, is discussed more systematically and generalized for reactive collision systems involving more than one configuration of reactant and product molecules, explicitly taking account of the conservation of the overall nuclear spin symmetry as well as the conservation of the total nuclear spin angular momentum, under the assumption of no nuclear hyperfine interaction. The values of SMP once calculated can be used for any system of identical nuclei of any spin as long as the system has the corresponding nuclear spin symmetry. The values of SMP calculated for simple systems can also be used for more complex systems containing several kinds of identical nuclei or various isotopomers. The generalized formulation of statistical scattering theory which can easily represent various rearrangement mechanisms is also presented.

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“…16 The tube was immersed in a cryogen such as liquid nitrogen or liquid hydrogen ͑for higher para enrichments͒, and the backing pressure was set such that the H 2 was forced to flow through the catalyst.…”

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confidence: 99%

Producing and quantifying enriched para-H2

Tom

Bhasker

Miyamoto

et al. 2009

Review of Scientific Instruments

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The production of enriched para-H(2) is useful for many scientific applications, but the technology for producing and measuring para-H(2) is not yet widespread. In this note and in the accompanying auxiliary material, we describe the design, construction, and use of a versatile standalone converter that is capable of producing para-H(2) enrichments of up to > or = 99.99% at continuous flow rates of up to 0.4 SLM. We also discuss para-H(2) storage and back conversion rates, and improvements to three techniques (thermal conductance, NMR, and solid hydrogen impurity spectroscopy) used to quantify the para-H(2) enrichment.

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Grundlagen der Photochemie.

Cited by 26 publications

References 0 publications

Nuclear spin conversion of methane in solid parahydrogen

Nuclear spin conversion of methane in solid parahydrogen

Nuclear spin selection rules for reactive collision systems by the spin-modification probability method

Producing and quantifying enriched para-H2

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