Precision test of bound-state QED at intermediate Z with kaonic neon

We report Dirac-Fock calculations of transition energies for kaonic neon. For the most intense line, the 7–6 transition, the calculated energy is 9450.28 eV, which includes a bound-state quantum electrodynamics (BSQED) contribution of 12.66 eV. This is in excellent agreement with the recent SIDDHARTHA-2 measurement at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mi>DA</a:mi> <a:mi mathvariant="normal">Φ</a:mi> <a:mi>NE</a:mi> </a:mrow> </a:math> of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mn>9450.23</c:mn> <c:mo>±</c:mo> <c:mn>0.37</c:mn> <c:mspace width="0.16em"/> <c:mo>(</c:mo> <c:mi>stat</c:mi> <c:mo>.</c:mo> <c:mo>)</c:mo> <c:mo>±</c:mo> <c:mn>1.50</c:mn> <c:mspace width="0.16em"/> <c:mo>(</c:mo> <c:mi>syst</c:mi> <c:mo>.</c:mo> <c:mo>)</c:mo> <c:mspace width="0.16em"/> <c:mi>eV</c:mi> </c:mrow> </c:math> . With the quantum electrodynamics contribution far exceeding experimental uncertainty, these results establish kaonic atoms as sensitive platforms for precision tests of BSQED in intermediate-Z systems.