A simple realistic and precise empirical intermolecular potential is proposed for helium. It possesses nearly the correct Hartree–Fock repulsion as well as the correct long range behavior. It was fitted to recent accurate intermediate temperature second virial coefficients and thermal conductivity data as well as high temperature viscosity values. It is able to predict second virial coefficients over an extended temperature range from 1.5 to 1475 K. Above 100 K it reproduces substantially all of the transport properties to within experimental error in a manner superior to all other potentials in existence. Below 100 K where the transport data are less reliable, it produces a good representation of the isotopic differences in the viscosity. It also predicts differential cross sections reasonably well. In spite of a few remaining discrepancies, when all the different macroscopic properties are considered, the potential produces the best representation of the helium interaction available at this time.

No abstract

Second virial coefficient data and viscosity were used to evaluate effective isotropic intermolecular potential functions proposed in the literature for sulfur hexafluoride. It was found that none of the potentials could predict the properties simultaneously. We have constructed a Morse–Morse–Spline–van der Waals (MMSV) potential which satisfactorily correlates second virial coefficient and viscosity data at the same time.

The groundwave portion of atmosp heric wavefor ms was examin ed to determine vario us characteristics of the radiation field from li ghtn in g di scha rges. Sixty-n ine represe ntative waveforms were' selected from 1,029 atmospherics from 21 thunderstor ms in the Oklahoma a nd No rt h Texas area. The average ampli t ude and pha e spectra, from 1 kc/s to 100 kc/s, are presented for several groups of atmospherics hav ing distin guis hable cha racteristics. Various relationships involving the total rad iated e nergy, peak fi eld strength, first half cycle length, spectral ampli tude peak and freque nc y of spectra peak are prese nted. The " normal" type of at mosplleric, composin g 86 percent of the total, is predominately of positive ini t ia l polarity, has a s pectrum peak near 5 kc/s and has well defin ed relationships betwee n t he parameters me ntioned above. All "other" types of atmospherics are predomin ately of negative initial polar ity, have a spectrum peak from less than 1 kc/ to 18 kc/s and have no well defined relationships between the vari ous p a rameters.