In (α,xn) and (12C, 5n) in-beamγ-ray experiments with pulsed beams the decay of the 560 ns high-spin isomer in147Gd has been investigated. Extensive coincidence measurements identified in the isomeric decay more than eightyγ-rays which almost all were placed in the level scheme. Of crucial importance for establishing the highly complex decay was the comparison of data from the different reactions and the identification of transitions which bypass the 27 ns isomer at 3.58 MeV. Our data determine the excitation of the 560 ns isomer as 8.588 MeV and suggest 47/2 as its most probable spin.
An experiment is described, where elements that can be procured in thin foils, are irradiated with monoenergetic gamma quanta from the reaction 7Li(p,γ)8Be. The energies of the photoprotons from the foil are measured with silicon surface barrier detectors. The conditions under which these protons give information about proton hole states are discussed. Results from runs on a foil of natural copper are given.
Using the reactor-produced lanthanum isotope 57 137 La, the highly enriched rare 57 138 La and the stable 57 139 La, the isotope shift has been measured in five lines of the La I-spectrum with the aid of a pressure-scanned Fabry-Pérot interferometer. The isotope shift data obtained show surprisingly large specific mass effects, arising from configuration mixing of levels with a 4f electron involved. The changes in mean square charge radiusδ〈r2〉 of these nuclei extracted from the experimental isotope shift constants Cexp are compared with the corresponding values for the isotonic barium nuclei, where similar anomalies in the isotope shifts occur.
The structure of the natural and unnatural parity states of the15N-15O mirror pair, as well as theT=3/2 analogue states of15C, is discussed in terms of shell model calculations with a modified surface delta two-body interaction. The inert core is recomposed from4He to12C and the configuration space is systematically expanded to allow for an increasing number of particle excitations from the 1p into the 2s-1d shell. The relative importance of the 2s 1/2, 1d 5/2 and 1d 3/2 orbitals are evaluated. Some electromagnetic properties of levels are also calculated.
Solutions of the generalized theory are obtained which are consistent with the previous work on energy transfer measurements. They also agree with the measurements of turbulent energy spectrum for wave numbers in the universal equilibrium range.
The time differential perturbed angular correlation technique has been used to measure the electric fieldgradient (EFG) at the site of181Ta impurities in the heavy Rare Earth metals Gd, Tb, Dy, Ho and Er at room temperature. It is found that the ratio α ≡ ¦V zz eff /V zz lat ¦ between the measured EFGV zz eff and the lattice EFGV zz lat , which is known from lattice sum calculations, is in the order of α≃300, suggesting that an important contribution to the EFG is due to electrons localized at the impurity. The ratio α is not constant throughout the Rare Earth series. It decreases from Gd to Tb and increases between Tb and Er. This behaviour is compared to the results of a previous investigation with the impurity Cd in the same hosts.
The rotational properties of non-axial nuclei are studied by means of the generator coordinate method, and in particular it is shown that using the angular momentum projection technique and assuming the Gaussian overlap approximation for the Hamiltonian and overlap matrix elements, the Hill-Wheeler integral equation may be transformed into an equivalent Schrödinger equation for a non-axial rotator.
Using a decoupling scheme for the second order Green's function expressions are derived for the dynamical susceptibility and for spin wave frequencies above the transition temperatureT c. The possible damping of the spin waves is discussed.
When superconductivity of the first kind in a cylinder is strongly suppressed by a current, only superconducting fluctuations exist near the sample axis. This one-dimensional “mixed” state is destroyed near some critical current. The width of the transition region is the smaller the purer the sample.
Attention is called to the paucity of experimental information about the fields and charged particle number densities in the transitional regimes between simple and dense discharges, for small electrode separation, and simple and normal discharges for large electrode separation, and to the occurrence of radial constriction in the latter some-what like that in normal discharges. Methods are suggested for ascertaining the nature of the negative glows and cathode dark spaces observed, and conjectures made as to the results likely to be found. It is also suggested that constriction of the transitional and normal discharges is due to essentially the same cause.
The theory of the longitudinal magnetoresistance at high magnetic fields and low temperatures is reformulated to incorporate screened impurities or a random potential of rather arbitrary shape. Analytical expressions are derived for the density of states, the chemical potential, the quasi particle damping and the longitudinal conductivity. They include vertex corrections and are valid from the higher field Shubnikov-de Haas regime up to arbitrarily high fields. The theory contains no adjustible parameter except the potential correlation function. InSb is studied as an example and a comparison with the experiment yields field dependent screening parameters.
Doppler-broadened level-crossing curves have been observed in selective reflection, showing an additional crossing effect between Zeeman-sublevels of different isotopes. Pressure-broadening by foreign gases has also been studied.
The electrical and thermal conductivities of air contaminated with electrode metal vapour from copper electrodes has been measured up to 8200 °K at atmospheric pressure using a modified form of Maecker's wall stabilized arc with a stabilizing hole 5 mm in diameter. The results of the study are compared with those of an uncontaminated arc in air. Both the conductivities are much greater than those for uncontaminated arc in air. This is believed to be due to the increased electron density by virtue of the lower ionization potential of copper. Energy transport by radiation is neglected in this study.
The reflection coefficients for various heavy ion potentials are calculated in an approximation which includes a wave mechanical surface reflection term in addition to the semiclassical WKB-term. For potentials which are deep and strongly absorbing in the interior of the potential well reflection from the surface gives the dominant contribution to the reflection coefficients with small angular momenta. For shallow potentials these two terms are still not sufficient for the calculation of the reflection coefficients, indicating that higher order reflections are important.
A chemical reaction model is discussed whose steady states show the phenomenon of non equilibrium phase transition of first order. If diffusion occurs, coexistence of two or three phases in different domains is possible. Phase diagram with two or three critical points and a triple point is obtained. For plane boundary layers between the domains the coexisting states are found by a construction analogous to the Maxwellian construction of vapor pressure of a Van der Waals gas. For spherical domains the coexistence dates change with radius analogously as vapor pressure of droplets or bubbles.
The mean lives of a number of energy levels in Co I and Co II have been measured. Particular attention has been paid to the energy loss incurred by the ions in the foil, which was found to be somewhat larger than the loss forecast by Lindhard's theory.A-values derived for Co I (using relativegA-values from the literature) are found to be significantly lower than those reported previously by other authors. Fair agreement is obtained for Co II with theA-values forecast by Warner. The Co IA-values indicate that the cobalt solar abundance given by Goldberget al. (LogNCo=4.64) should be increased to about 4.9.
A variational calculation has been performed for the elastic e+-He scattering at energies below 16 eV. Partial waves up toL=3 are included. The trial functions contain distortions which take into account virtual positronium formation. The results of the calculation show good agreement with experimental cross section data.
A theory of a detuned single mode laser near threshold is given using the Fokker-Planck equation technique. The Fokker-Planck equation is solved by an eigenfunction expansion. The eigenfunctions and the corresponding eigenvalues are determined by a nonhermitian operator and are calculated numerically in the threshold region. The dependence of the linewidth from the detuning is shown. In the intensity distribution the detuning enters only via a change of the scaling parameter. For the linewidth, however, an additional broadening is found. Finally it is shown that in certain cases the correlation function must not be approximated by a single exponential term.
We investigate the possible occurrance of partially depaired states in superconducting intercalated layered systems. Those states are discussed as a possible explanation of the high critical fields found in some of these materials. It is shown that the Chandrasekhar-Clogston limit does not apply to those states mentioned above and that the maximum field compatible with superconductivity is a sensitive function of the shape of the Fermi surface. Mean free path and spin-orbit effects on the partially depaired state are investigated. An experiment is proposed to decide between the partially depaired state and a large spin-orbit scattering rate as possible explanations for the large critical fields.
Competing interactions, responsible for two differently ordered phases in the ammonium halides, also cause the coexistence of different short range correlations in the disordered state. Correlations of the nonordering density may be the reason for tricritical behavior or even a discontinuity of the transition. Molecular field theory neglects all correlations and thus is unable to provide an appropriate description of NH4Cl under pressure and of NH4Cl-NH4Br mixtures. In this paper a phase diagram is obtained for the ammonium halides in first Bethe approximation from a simplified model Hamiltonian with competing interactions. A tricritical point is found for the order-disorder transition into the uniform or “ferromagnetic” phase as well as for the transition into the “antiferromagnetic” phase.
