Showing papers by "Lawrence Berkeley National Laboratory published in 1971"

Zeeman Effect in Porphyrins: Zero‐Field Splitting of the Excited Electronic States

Abstract: Recent experimental studies have reported anomalous and contradictory results for the absorption of left and right circularly polarized light (LCPL and RCPL) by zinc and magnesium coproporphyrins in the presence of a magnetic field: for both compounds, the absorption bands for right and left circularly polarized light have distinctly different shapes at room temperature; at 77°K unexplained shoulders appear in the absorption spectra for both polarizations for the magnesium but not for the zinc compound; the value of the angular momentum of the lowest energy excited state computed from the separation of the peaks of the LCPL and RCPL absorption bands differs from the value obtained from magnetic circular dichroism (MCD) experiments by nearly 50%; no shape anomalies were observed in the MCD spectra. We derive a general solution for the mixing of two states by a magnetic field and show that all of the anomalous experimental data are explained if (a) the presumably degenerate pair of excited states are split ...

Structure and mechanical properties of Fe−Cr−C−Co steels

Abstract: As part of a continuing program concerning the microstructures and mechanical properties of steels in which particular attention is given to transformation substructures, the present work is concerned with martensite and bainite in Fe−Cr−C steels with and without cobalt. Although cobalt raises theM s temperature it does not affect the extent of twinning for the same carbon level and so M s temperature alone does not control transformation substructure. Thus cobalt is not effective in retaining dislocated martensite as carbon is increased and in this regard cobalt is not beneficial to toughness. TheM s temperatures of the steels were relatively high and hence isothermal transformation yielded mixtures of bainites and tempered martensite depending on the temperature of transformation. The mechanical properties of the isothermally transformed steels were inferior to those of the tempered steels due to the interference of upper bainite or (tempered) martensite during the isothermal transformation. Thus, in the steels having highM s temperatures the twinning tempered martensitic structure had relatively better mechanical properties compared to the isothermally transformed steels. Attempts to produce desirable autotempered structures by air cooling (single heat treatments) were not successful and did not improve the mechanical properties since the structure consisted of a mixture of bainite and martensite.

Diffraction Radiation by a Line Charge Moving past a Comb: A Model of Radiation Losses in an Electron Ring Accelerator

Abstract: A calculation is given of the radiated‐energy loss from a charged rod which moves at constant speed past an infinite set of parallel semi‐infinite conducting plates of infinitesimal thickness, with the rod taken parallel to and at a fixed distance from the plate edges. The problem is analyzed using the Wiener‐Hopf technique, and the resulting formulas are evaluated analytically in the limits of high rod speed and low rod speed, and compared with numerical evaluation over the full range of speeds.

Heat capacity of liquid bismuth

Abstract: The true heat capacity of liquid bismuth was measured from within three tenths of a ,degree of :the melting point',.(544. 5°K) to .801. SOK \\ ' by a method of mixtures using a liquid bismuth calorimeter, The results show a decreas~ in heat capacity with increasing temperature, This is in agreeni~ritwith'a trend which has been observed fOr the ) . heat capacities of other liquid metals.

Another bound on the absorptive part of elastic scattering amplitudes

Abstract: Via Lagrange multipliers for inequality constraints, an upper bound on the absorptive part of the elastic scattering amplitudes is derived assuming unitarity, a fixed total and elastic cross section, and the condition that the partial waves decrease monotonically with increasing angular momentum. Numerical results are given.

Can a pulse excitation smaller than kT be detected

Abstract: A ‘1kT-pulse’ excitation of a high-Q-factor LC ringing circuit is defined, and a filter configuration is described which allows the detection of such a pulse with good s.n.r. (signal/noise ratio) and excellent τr, (resolving time). S.N.R.s considerably larger than unity were found experimentally, in reasonable agreement with theoretical calculations.

Light flash phenomenon seen by astronauts.

Abstract: The results from experiments conducted to characterize and elucidate light flashes seen by astronauts on Apollo 11, 12, 13, and 14 during transluna or transearth orbit are presented. The data show cosmic nuclei interacting with the visual apparatus causes the light flash phenomenon. The data also suggest that slow protons and helium ions with a stopping power greater than 10 KeV/micron will cause light flashes and streaks in the partially dark adapted eye. The effects of galactic cosmic nuclei interacting with man during long term missions are discussed.