Volume 24, Issue 1, January 1995
Index of content:
24(1995); http://dx.doi.org/10.1063/1.555972View Description Hide Description
The rotational‐torsional spectrum of the trans rotational isomer of ethyl alcohol was investigated in the 65–350 GHz frequency region. A total of 481 ground state transitions over a range of J and K a values up to 33 and 10, respectively, were measured and assigned. Doublets or triplets arising from the A and E torsional states of the v=0 torsional level of the three‐fold‐symmetric methyl internal rotation have been resolved in 168 of these transitions. Internal rotation theory predicts a significant number of c‐type E‐state transitions normally forbidden, but allowed when the rotational asymmetry operators mix E‐state rotational‐torsional levels. Over 40 of these transitions have been observed. The newly measured transitions, along with the results of many previous measurements, have been analyzed using an IAM internal rotation Hamiltonian and a Watson A‐reduced Hamiltonian to determine the rotational, centrifugal distortion, and torsional constants. The IAM analysis accounts for all of the analyzed transitions in the trans isomer, but for some applications the asymmetric rotor analysis is a satisfactory description of the molecule. The J and K a limits where the trans isomer can be analyzed without considering interactions with the gauche states are also discussed. Predicted frequencies for transitions unaffected by the gauche states are presented through 600 GHz using the constants determined by this work.
24(1995); http://dx.doi.org/10.1063/1.555977View Description Hide Description
All reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS‐90 temperature scale. The data extend over a temperature range from 238 to 873 K and over a pressure range from 0.1 MPa up to 1189 MPa. The evaluative part of this work includes a review of the different types of measurement techniques, and the corrections for frequency dependence due to the impedance of circuit components, and to electrodepolarization. It also includes a detailed assessment of the uncertainty of each particular data source, as compared to other sources in the same range of pressure and temperature. Both the raw and the corrected data have been tabulated, and are also available on diskette. A comprehensive list of references to the literature is included.
Theoretical Form Factor, Attenuation, and Scattering Tabulation for Z=1–92 from E=1–10 eV to E=0.4–1.0 MeV24(1995); http://dx.doi.org/10.1063/1.555974View Description Hide Description
Tables for form factors and anomalous dispersion are widely used in the UV, x‐ray, and y‐ray communities, and have existed for a considerable period of time. Much of the recent theoretical basis for these was contributed by Cromer, Mann, and Liberman while much of the experimental data were synthesized by Henke et al. More recent developments in both areas have led to new and revised tables. These works have employed numerous simplifications compared to detailed relativistic S‐matrix calculations; the latter do not lend themselves to convenient tabular application for the range of Z and energy of general interest. Conversely, the former tables appear to have large regions of limited validity throughout the range of Z and energies, and in particular have important limitations with regard to extrapolation to energies outside tabulated ranges. In the present study, the primary interactions of x‐rays with isolated atoms from Z=1 (hydrogen) to Z=92 (uranium) are described and computed within a self‐consistent Dirac–Hartree–Fock framework. This has general application across the range of energy from 1–10 eV to 400–1000 keV, with limitations (described below) as the low‐ and high‐energy extremes are approached.
Tabulations are provided for the f 1 and f 2 components of the form factors, together with the photoelectric attenuation coefficient for the atom, μ, and the value for the K‐shell, μK, as functions of energy and wavelength. Also provided are estimated correction factors as described in the text, conversion factors, and a simple estimate for the sum of the scattering contributions (from an isolated atom). The method used herein is primarily theoretical and considers intermediate assumptions which limit the precision and applicability of previous theoretical tabulations. Particular concern involves the application of the dispersion relation to derive Re(f) from photoelectric absorption cross‐sections. The revised formulation presented here explicitly avoids most of the limitations of previous works. Revised formulae can lead to significant qualitative and quantitative improvement, particularly above 30–60 keV energies, near absorption edges, and at 0.03 keV to 3 keV energies. Recent experimental syntheses are often complementary to this approach. Examples are given where the revised theoretical tables are in better agreement with experiment than are those based on experimental syntheses.