RADIATIONLESS ANNIHILATION OF POSITRONS IN LEAD.

摘要: A process of positron annihilation without emission radiation, radiationless or zero-quantum annihilation, has been investigated experimentally. theory for this phenomenon also developed. The 300-keV positrons were focused on a thin lead target by the use Siegbahn-Sl\"atis intermediate-image spectrometer mounted with ${\mathrm{Na}}^{22}$ as source. shell electrons ejected from foil observed lithium-drifted silicon detector immediately behind foil. We have small peak in expected energy region electron spectrum. This attributed to effect thickness examined carefully an important factor influencing our observations. Using experimental data obtained, we attempted estimate total cross section lead. Our result is ${\ensuremath{\sigma}}_{\mathrm{exptl}}=0.8_{\ensuremath{-}0.3}^{}{}_{}{}^{+0.4}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}$ ${\mathrm{cm}}^{2}$ sum those $K\ensuremath{-}K$, $K\ensuremath{-}L$, $K\ensuremath{-}M$, and $L\ensuremath{-}L$ pairs atom positrons. calculated obtained ${\ensuremath{\sigma}}_{\mathrm{calc}}=0.727\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}$ ${\mathrm{cm}}^{2}$. value agreement within error. present work established evidence mode furthered understanding process.