Wolfgang Bühring

Beta decay theory using exact electron radial wave functions: (III). The influennce of screening

Abstract In order to investigate the influence of screening on beta decay functions, a method -based on power series expansions - is described for calculating continuum state solutions of the Dirac radial equations containing a sufficiently genral potential. Tables of beta decay functions for beta spectra, electron polarization and beta-gamma correlations calculated with a screened potential are given. Ratios of these values to values without screening also included.

Nuclear beta decay

Abstract New formulae for nuclear beta decay are derived by using a modified expansion of the electron radial wave functions. This expansion is obtained by means of the integral equations which correspond to the Dirac radial differential equations. As a consequence new types of form factor coefficients or nuclear matrix elements occur which depend on the shape of the nuclear charge distribution. The implications of the new formulae for the analysis of experiments are discussed. The sensitivity to the detailed shape of the charge distribution turns out to be weak usually, even in the case of non-unique forbidden transitions. An elementary treatment of the induced interactions leads in a simple way to the formulae which express the form factor coefficients in terms of coupling constants and nuclear matrix elements. Expressions are given for the single-particle values of all the nuclear matrix elements in terms of radial integrals. References

Elastic electron scattering experiments on Be and C at 53 MeV and their analysis using an improved phase-shift method

Abstract Cross sections for elastic electron scattering from beryllium were measured relative to carbon at the Darmstadt electron linear accelerator. The experimental data were analysed with an improved phase-shift method which is described in detail. Using a recently obtained rms radius R m (C) = 2.42±0.04fm for carbon (natural isotopic mixture), the beryllium rms radius is R m (Be) = 2.46±0.09 fm, and R m (Be) in m(C) = 1.015±0.024. Using these results, a new analysis of a recent experiment yields R m (Ti) = 3.56±0.04 fm for titanium (natural isotopic mixture). This radius is compared to that deduced from the muonic 2p-1s energy.

BETA DECAY THEORY USING EXACT ELECTRON RADIAL WAVE FUNCTIONS. IV. INDUCED EFFECTS

Abstract Beta decay formulae derived in previous papers are re-interpreted on the basis of a quite general V-A interaction which takes into account all effects induced by the strong interaction. As an example of application the induced pseudoscalar interaction is investigated in some detail.

Polarization of slow electrons (100–2000 ev) elastically scattered from heavy atoms

The angular and energy dependence of the Mott polarization for slow electrons is explained in terms of the complex zeros of the scattering amplitudef(z), wherez is the cosine of the scattering angle. The trajectories in the complexz-plane, on which the zeros move if the energy is varied, are shown in the case of scattering from mercury atoms. The properties of these trajectories imply that there are, in fact, certain combinations of energy and angle, for which total polarization occurs. Calculations for target atoms lighter than mercury show, that the number of such combinations becomes smaller and the corresponding energy values are shifted to lower energies. The possibility is also discussed to extract the complex zeros and the other relevant parameters from the experimental data rather than from theoretical calculations, which to some extent are sensitive to the model of the atomic potential.

Relativmessung der Elektronenpolarisation beimxβ-Zerfall: RaE(Bi210)-P32

An apparatus is described for comparing the longitudinal polarization valuesP ofβ-particles from different emitters by the method of double scattering. For RaE(Bi210) and P32 we have measured the ratio of polarization values to be P(RaE)/ P(P32)=0·757±0·022 at 540 keV. This is in good agreement with previous measurements. Ratios of matrix elements are determined from polarization and spectrum shape data of RaE, but these values are not reliable because the spectrum shape shows a systematic discrepancy between theory and experiment below 200 keV. A discussion of electron polarization and spectrum shape data of P32 shows that deviations of polarization from the allowed value are probably very small.An appartus is described for comparing the longitudinal polarization values P of BETA particles from different emitters by the method of double scatiering. For RaE(/sup 210/Bi) and /sup 32/P the ratio of polarization values was measured to be P(RaE)/ P(/sup 32/P) = 0 757 plus or minus 0.022 at 540 kev. This was in good agreement with previous measurements. Ratios of matrix elements were determined from polarization and spectrum shape data of RaE, but these values were not reliable because the spectrum shape showed a systematic discrepancy between theory and experiment below 200 kev. A discussion of electron polarization and spectrum shape data of /sup 32/P showed that deviations of polarization from the allowed value are probably very small. (auth)

Die Elektronenpolarisation beim β-Zerfall des RaE

ZusammenfassungMit kombinierter Vielfach- und Einzelstreuung wird die ElektronenpolarisationP des RaE durch Vergleich mit Tl204 und Y91 gemessen. Für den Mittelwert von

On the sensitivity of β-transitions to the shape of the nuclear charge distribution

P/\frac{v}{c}