Electron-capture decay of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mi>Tc</mml:mi> <mml:mprescripts/> <mml:none/> <mml:mn>98</mml:mn> </mml:mmultiscripts> </mml:math>

From simple symmetry and energy considerations it can be concluded that <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mmultiscripts> <a:mi>Tc</a:mi> <a:mprescripts/> <a:none/> <a:mn>98</a:mn> </a:mmultiscripts> </a:math> might undergo electron capture decay (EC). In this work we provide evidence for an EC decay of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mmultiscripts> <b:mi>Tc</b:mi> <b:mprescripts/> <b:none/> <b:mn>98</b:mn> </b:mmultiscripts> </b:math> measuring 2.67 g <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mi mathvariant="normal">K</c:mi> <c:mo>[</c:mo> <c:mrow> <c:mi>Tc</c:mi> <c:msub> <c:mi mathvariant="normal">O</c:mi> <c:mn>4</c:mn> </c:msub> </c:mrow> <c:mo>]</c:mo> </c:mrow> </c:math> that contains approximately 1 GBq of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mmultiscripts> <f:mi>Tc</f:mi> <f:mprescripts/> <f:none/> <f:mn>99</f:mn> </f:mmultiscripts> </f:math> . By use of a lead shielding for the sample, it was possible to identify the coincident <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mrow> <g:mn>4</g:mn> <g:mo>+</g:mo> <g:mo>→</g:mo> <g:mn>2</g:mn> <g:mo>+</g:mo> </g:mrow> </g:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mrow> <h:mn>2</h:mn> <h:mo>+</h:mo> <h:mo>→</h:mo> <h:mn>0</h:mn> <h:mo>+</h:mo> <h:mi>γ</h:mi> </h:mrow> </h:math> transitions in the daughter nuclide <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mmultiscripts> <i:mi>Mo</i:mi> <i:mprescripts/> <i:none/> <i:mn>98</i:mn> </i:mmultiscripts> </i:math> at the University of Cologne's Cologne Clover Counting setup of the Institute for Nuclear Physics. For the first time, the EC/ <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:msup> <j:mrow> <j:mi>β</j:mi> </j:mrow> <j:mo>−</j:mo> </j:msup> </j:math> branching ratio of 0.29(3)% was determined directly. With a <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mrow> <k:mo form="prefix">log</k:mo> <k:mi>f</k:mi> <k:mi>t</k:mi> </k:mrow> </k:math> of 14.21(7) this decay does almost tie with the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mo form="prefix">log</m:mo> <m:mi>f</m:mi> <m:mi>t</m:mi> </m:mrow> </m:math> of the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"> <o:mmultiscripts> <o:mi>Cl</o:mi> <o:mprescripts/> <o:none/> <o:mn>36</o:mn> </o:mmultiscripts> </o:math> EC decay [14.23(1)] for the same highest second forbidden nonunique transition.