摘要:

In this compilation we have used data from some 20 references, only two of which were available to C. E. Moore for her 1949Atomic Energy Levelstables. The new compilation thus includes significant revisions, extensions, and improvements of the earlier data for configurations of the types1s22snland1s22pnland also extends the energy range to higher configurations, including those involving 1selectron excitation. The observed wavelengths for some 200 lines are given with their energy-level classifications. The wavelength measurements, which extend from 89 to 31 780 Å, were obtained from emission spectra of hollow-cathode and arc discharges, beam-foil spectra, and far-ultraviolet photoabsorption spectra. In addition to the energy levels derived from these spectra, we include levels obtained from multiphoton resonance-ionization mass spectrometry and projectile-Auger spectroscopy. We have evaluated a number of levels by using series formulas and/or theoretical results; these levels are more accurate than values derived from available wavelength measurements. Wavelengths calculated from energy-level differences are given for all lines; these “Ritz” wavelengths are more accurate than the observed values wherever the differences are significant. ©1997 American Institute of Physics and American Chemical Society.

ISSN:0047-2689    

DOI:10.1063/1.555999

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A self-consistent, single-valued representation of the major physical, mechanical, and thermal properties of a sintered &agr;-SiC is presented. This comprehensive set of properties is achieved by focusing on a narrowly defined material specification in which boron and carbon are used as sintering aids to produce a dense ceramic (⩾98&percent; of the theoretical maximum density) with a grain size of (6±2) &mgr;m. Such a representation is highly desirable in applications of concurrent engineering practices and for the increasing use of electronic processing of product specifications. ©1997 American Institute of Physics and American Chemical Society.

ISSN:0047-2689    

DOI:10.1063/1.556000

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article, available information on the cross sections and rate coefficients for collisional interactions of dichlorodifluoromethane(CCl2F2)with electrons is critically evaluated and synthesized. This gas has many industrial uses and is of atmospheric and environmental interest. The CCl2F2molecule fragments rather extensively under electron impact, principally via dissociative ionization and dissociative attachment; the latter process is temperature dependent. Information is presented and discussed on: (1) electron scattering processes [cross sections for total electron scattering, momentum transfer, differential elastic electron scattering, integral elastic electron scattering, and inelastic electron scattering for rotational and vibrational (direct and indirect) excitation]; (2) electron impact ionization (cross sections for total, partial, and double ionization and coefficients for electron impact ionization); (3) electron attachment (electron attachment cross sections and rate constants and their energy and temperature dependencies, electron attachment coefficients, dissociative attachment fragment anions, and negative ion states); (4) optical emission under electron impact, and (5) electron transport coefficients (electron drift velocity and ratio of transverse electron diffusion coefficient to electron mobility). Based upon the assessment of published experimental data, recommended values of various cross sections and rate coefficients are generated in graphical and tabular form. Areas where additional data are needed are identified, such as the measurement of the cross sections for momentum transfer and electron impact dissociation of CCl2F2into neutral species.©1997 American Institute of Physics and American Chemical Society.

ISSN:0047-2689    

DOI:10.1063/1.555995

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The biennial review of atomic weight,Ar(E), determinations and other cognate data has resulted in changes for the standard atomic weight of 21 elements. The five most significant changes are: boron from10.811±0.005to10.811±0.007;carbon from12.011±0.001to12.0107±0.0008;arsenic from74.92159±0.00002to74.92160±0.00002;cerium from140.115±0.004to140.116±0.001;and platinum195.08±0.03to195.078±0.002.An annotation for potassium has been changed in the Table of Standard Atomic Weights. To eliminate possible confusion in the reporting of relative lithium isotope-ratio data, the Commission recommends that such data be expressed using7Li/6Liratios and that reporting using6Li/7Liratios be discontinued. Because relative isotope-ratio data for sulfur are commonly being expressed on noncorresponding scales, the Commission recommends that such isotopic data be expressed relative to VCDT (Vienna Can˜on Diablo Troilite) on a scale such that34S/32Sof IAEA-S-1 silver sulfide is 0.9997 times that of VCDT. Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on oxygen are included in this article for the information of the interested scientific community. ©1997 American Institute of Physics and American Chemical Society.

ISSN:0047-2689    

DOI:10.1063/1.556001

出版商:AIP    

年代:1997

数据来源: AIP