Measurement of the fluorescence decay rate of 2 PJ3 positronium

The fluorescence decay rate of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>2</a:mn><a:mo> </a:mo><a:mmultiscripts><a:msub><a:mi>P</a:mi><a:mi>J</a:mi></a:msub><a:mprescripts/><a:none/><a:mn>3</a:mn></a:mmultiscripts></a:mrow></a:math> positronium (Ps) atoms <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mo>[</b:mo><b:msub><b:mi mathvariant="normal">Γ</b:mi><b:mi>fl</b:mi></b:msub><b:mo>]</b:mo></b:math> has been experimentally determined using a Stark-mixing technique. Ground-state Ps atoms were optically excited in an electric field to states containing both <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mn>2</d:mn><d:mo> </d:mo><d:mmultiscripts><d:msub><d:mi>P</d:mi><d:mi>J</d:mi></d:msub><d:mprescripts/><d:none/><d:mn>3</d:mn></d:mmultiscripts></d:mrow></d:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mn>2</e:mn><e:msup><e:mspace width="0.16em"/><e:mn>3</e:mn></e:msup><e:msub><e:mi>S</e:mi><e:mn>1</e:mn></e:msub></e:mrow></e:math> components. The relative state populations were controlled via an applied mixing electric field, and a larger, pulsed, electric field was used to induce rapid quenching of the system after a fixed time delay. The dependence of the quenching signal on the mixing field strength was used to determine the relative and populations of the mixed states, whose decay rates are determined by the intrinsic self-annihilation and fluorescence decay rates. The measurements were compared to a trajectory simulation and Stark-mixing model, using the fluorescence decay rate as a free parameter. By finding the best agreement between the data and simulations we obtain <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:msub><g:mi mathvariant="normal">Γ</g:mi><g:mi>fl</g:mi></g:msub><g:mo>=</g:mo><g:mn>299</g:mn><g:mo>±</g:mo><g:mn>25</g:mn><g:mspace width="4pt"/><g:mi>µ</g:mi><g:msup><g:mrow><g:mi mathvariant="normal">s</g:mi></g:mrow><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup></g:mrow></g:math>, which is consistent with the mean theoretical value of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mn>313.343</k:mn><k:mspace width="0.16em"/><k:mo>±</k:mo><k:mn>0.003</k:mn><k:mspace width="0.16em"/><k:mi>µ</k:mi><k:msup><k:mrow><k:mi mathvariant="normal">s</k:mi></k:mrow><k:mrow><k:mo>−</k:mo><k:mn>1</k:mn></k:mrow></k:msup></k:mrow></k:math>. Published by the American Physical Society 2024