摘要:

The rotational‐torsional spectrum of thetransrotational isomer of ethyl alcohol was investigated in the 65–350 GHz frequency region. A total of 481 ground state transitions over a range ofJandKavalues up to 33 and 10, respectively, were measured and assigned. Doublets or triplets arising from theAandEtorsional states of thev=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 ofc‐typeE‐state transitions normally forbidden, but allowed when the rotational asymmetry operators mixE‐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 WatsonA‐reduced Hamiltonian to determine the rotational, centrifugal distortion, and torsional constants. The IAM analysis accounts for all of the analyzed transitions in thetransisomer, but for some applications the asymmetric rotor analysis is a satisfactory description of the molecule. TheJandKalimits where thetransisomer can be analyzed without considering interactions with thegauchestates are also discussed. Predicted frequencies for transitions unaffected by thegauchestates are presented through 600 GHz using the constants determined by this work.

ISSN:0047-2689    

DOI:10.1063/1.555972

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

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reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS‐90 temperature scale.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 electrode polarization. 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.

ISSN:0047-2689    

DOI:10.1063/1.555977

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

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 Henkeetal. 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 ofZand energy of general interest. Conversely, the former tables appear to have large regions of limited validity throughout the range ofZand 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 atomsZ=1 (hydrogen) toZ=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 thef1andf2components of the form factors, together with the photoelectric attenuation coefficient for the atom, &mgr;, and the value for the K‐shell, &mgr;K, 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.

ISSN:0047-2689    

DOI:10.1063/1.555974

出版商:AIP    

年代:1995

数据来源: AIP