9 research outputs found
Valence electronic structure of Mn in undoped and doped lanthanum manganites from relative K x-ray intensity studies
Relative x-ray intensities of in , , and
( = , , and ) systems have been
measured following excitation by 59.54 keV -rays from a 200 mCi
Am point-source. The measured results for the compounds deviate
significantly from the results of pure . Comparison of the experimental
data with the multiconfiguration Dirac-Fock (MCDF) effective atomic model
calculations indicates reasonable agreement with the predictions of ionic model
for the doped {manganites except} that the electron doped
and hole doped compounds
show some small deviations. The results of and deviate
considerably from the predictions of the ionic model. Our measured
ratio of in cannot be explained
as a linear superposition of ratios of for the end
members which is in contrast to the recent proposal by Tyson et al. from their
spectra.Comment: 14 pages, 4 figures. to appear in NIM-B.Please send an e-mail for
figure
Search for a heavy neutrino in the β-decay of <SUP>35</SUP>S
Recent experimental evidence suggests that the neutrino (strictly, an antineutrino) emitted in the β-decay of tritium is a mixture of two mass eigen states |<SUB>v1</SUB> and |<SUB>v2</SUB> where |<SUB>ve</SUB>=cosθ |<SUB>v1</SUB> + sinθ |<SUB>v2</SUB> with m<SUB>v1</SUB><50 eV and m<SUB>v2</SUB>=17.1±0.2 keV and sin<SUP>2</SUP>θ =0.03. This conclusion is based on the observation of a 'kink' in the Fermi-Kurie plot of the electron energy spectrum at an energy 17.1 keV below the end point. Such an observation, if confirmed, will have far-reaching consequences in cosmology and particle physics. In the experiment reported here, a search was made for such an admixture in the β-decay of <SUP>35</SUP>S. We fail to confirm the presence of mixing of neutrinos with mass 17.1 keV and place an upper limit on such an admixture of 0.6% (90% confidence level)