ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTWhy atoms recombine more slowly as the temperature goes upHuw O. PritchardCite this: Acc. Chem. Res. 1976, 9, 3, 99–105Publication Date (Print):March 1, 1976Publication History Published online1 May 2002Published inissue 1 March 1976https://pubs.acs.org/doi/10.1021/ar50099a004https://doi.org/10.1021/ar50099a004research-articleACS PublicationsRequest reuse permissionsArticle Views80Altmetric-Citations46LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Abstract Die Ungleichgewichts‐Geschwindigkeitskonstanten der Dissoziation von H 2 und D2 scheinen sich bei niedrigen Temperaturen einem über die Rotationszustände gemittelten Gleichgewichtsausdruck anzupassen.
The thermal isomerization of cy clopropane to propylene is a homogeneous unimolecular reaction at 490° C and at pressures down of 0·007 cm. The rate constant of the unimolecular reaction falls off by a factor of ten as the pressure in the reaction system is decreased from 8·4 to 0·007 cm. The results are compared with various theories of quasi-unimolecular reactions. The addition of a non-reacting gas to the system counteracts the falling off. The relative efficiencies of a number of gases for maintaining the unimolecular rate constant have been measured.
ADVERTISEMENT RETURN TO ISSUEPREVArticleThe Determination of Electron Affinities.H. O. PritchardCite this: Chem. Rev. 1953, 52, 3, 529–563Publication Date (Print):June 1, 1953Publication History Published online1 May 2002Published inissue 1 June 1953https://pubs.acs.org/doi/10.1021/cr60163a002https://doi.org/10.1021/cr60163a002research-articleACS PublicationsRequest reuse permissionsArticle Views726Altmetric-Citations241LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
The relationships between individual rotational or vibrational transition probabilities and the eigenvalues of the 172nd order relaxation matrix describing the rotation–vibration–dissociation coupling of ortho-hydrogen are explored numerically. The simple proportionality between certain transition probabilities and certain eigenvalues, which was found previously in the vibration–dissociation coupling case, breaks down. However, it is shown that at 2000°K the second smallest eigenvalue of the relaxation matrix (d n−2 ), hitherto regarded as determining the "vibrational" relaxation time, is related more to the transition probability assigned to the largest rotational gap which lies in the first (ν = 0 ↔ ν = 1) vibrational gap, i.e. to the transition ν = 0, J = 5 ↔ ν = 0, J = 7, than to anything else; this clearly supports an earlier suggestion that the transient which immediately precedes dissociation in a shock wave has to be regarded as a rotation–vibration relaxation time rather than a vibrational relaxation time. It is suggested that the Lambert–Salter relationships can be rationalized on this assumption.An analysis is then made of the energy uptake associated with each eigenvalue at three temperatures. At 500°K, the greatest energy increment is associated with two eigenvalues (d n−13 and d n−24 ) and can be characterized as essentially a rotational relaxation: the calculations confirm that the observed rotational relaxation time should first decrease and then increase with increasing temperature, as was recently found to be the case experimentally. At 2000°K, large energy increments are associated with several eigenvalues between d n−2 and d n−14 , and at 5000°K, with most of the eigenvalues d n−2 to d n−23 ; thus, the higher the temperature, the more complex is the (T–VR) rotation–vibration relaxation. Further, relaxation times for the same temperature measured by ultrasonic and shock-wave techniques need not agree.
The main products of decomposition of difluoroacetic acid in silica over the range 254–382 °C are carbon monoxide, formyl fluoride, carbon dioxide, silicon tetrafluoride, and difluoroacetyl fluoride. The initial step of decomposition is believed to be γ-elimination of hydrogen fluoride, followed mainly by the formation of carbon monoxide and of formyl fluoride, which itself decomposes. There is no evidence for dehydration to difluoroketen, nor for the formation of fluorocarbene.
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