Variational calculations are reported on the 1sns singlet and triplet states of the helium atom, up to and including n = 26. By suitable choice of terms in the expansion for the wave function, significant economies in computer time are possible, and we quote an example of a 12-term uncorrelated wave function which gives a lower energy than Pekeris' 220-term correlated wave function. The problems of extending these calculations to much higher n (e.g. n > 100) to include states of astrophysical interest are enumerated.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTHE DISSOCIATION OF DIATOMIC MOLECULES AND THE RECOMBINATION OF ATOMSH. O. PritchardCite this: J. Phys. Chem. 1962, 66, 11, 2111–2113Publication Date (Print):November 1, 1962Publication History Published online1 May 2002Published inissue 1 November 1962https://pubs.acs.org/doi/10.1021/j100817a008https://doi.org/10.1021/j100817a008research-articleACS PublicationsRequest reuse permissionsArticle Views154Altmetric-Citations16LEARN 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 options Get e-Alerts
The adiabatic coupling correction term [Formula: see text] has been evaluated by two methods, the one used by Kołos and Wolniewicz in 1964 and the one suggested by Kari, Chan, Hunter, and Pritchard in 1973. The difference between the two procedures for H 2 amounts to 0.04 cm −1 and is almost independent of internuclear separation in the range R = 1.0–1.8 a.u. Thus, the method of computing the Δ R -term does not affect the vibrational energy level spacings.
The rotation–vibration relaxation of a mixture of a diatomic gas (approximately simulating hydrogen) with an inert gas is studied both by direct integration, and by an approximate linearised normal-mode method. It is shown that although the linearised normal-mode approximation is a powerful aid to understanding these processes, its numerical accuracy is limited to high dilutions (e.g. 1% of X 2 in M) and to times shorter than the final relaxation time.Direct numerical integration of the relaxation equations for various mixture ratios shows that the plot of vibrational relaxation rate constant vs. mole fraction x is non-linear, and that the slope of this plot near x = 0 can be correlated with the rates of the R–R processes, not the V–V processes as is normally assumed. A brief discussion is presented of the conditions under which the linear mixture rule for relaxation is rigorously obeyed: as is the case for chemical reaction, these conditions are impossibly stringent.An appendix presents a comparison of the transition probabilities used in this series of papers with those recently obtained by Tarr and Rabitz for the relaxation of hydrogen in argon.
New turbojet-engine concept could reduce nitric oxide emissions to a level from one-fifteenth to as little as one three-hundredth that of conventional units. Multiple-stage combustor could overcome flame instability problems associated with previous low-flame-temperature systems. It operates in a relatively-simple adiabatic mode without elaborate fuel-flow and air circulation patterns.,
Estimates are made, by using BHandHLYP/6-311G** density functional molecular orbital theory, of the activation energies and frequency factors for the reaction of NO2 with methane, ethane, propane, isobutane, and benzene. For the aliphatic hydrocarbons, over the temperature range 600–1100 K, the rate of formation of a new isomer of nitrous acid, HNO2, is very similar to that for the formation of the common isomer, HONO. This complicates our description of the acceleration of spontaneous ignition of diesel fuels by organic nitrates. These rate data are used in a reduced kinetic model to examine the effect of NO2 upon the spontaneous ignition of some linear- and branched-chain aliphatic hydrocarbons. It is concluded that, under typical diesel engine operating conditions, the spontaneous ignition of linear-chain paraffins is accelerated by the presence of NO2, but may be retarded for heavily branched-chain isomers. An Appendix discusses the relative importance of tunnelling in hydrogen-transfer reactions.
Because of an editorial policy discouraging the presentation of experimental results in both graphical and tabular form, the primary rate constant data for the thermal isomerisation of cyclopropane in the fall-off region [53.P2] are only available in thesis form. One might have expected these results to have been superseded by now, but that has not happened, and Sowden's rather inaccessible thesis [54. S] remains the only source of these key data. In view of their continuing importance in the testing of unimolecular reaction theories, I am reproducing those results here (and also those of the cyclobutane reaction) for the convenience of future users.
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