Radiative lifetime of the A Π1/22 state in RaF with relevance to laser cooling

The radiative lifetime of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>A</a:mi><a:mspace width="0.16em"/><a:mmultiscripts><a:mi mathvariant="normal">Π</a:mi><a:mrow><a:mn>1</a:mn><a:mo>/</a:mo><a:mn>2</a:mn></a:mrow><a:none/><a:mprescripts/><a:none/><a:mn>2</a:mn></a:mmultiscripts></a:mrow></a:math> <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mo>(</d:mo><d:mi>v</d:mi><d:mo>=</d:mo><d:mn>0</d:mn><d:mo>)</d:mo></d:mrow></d:math> state in radium monofluoride (RaF) is measured to be 35(1) ns. The lifetime of this state and the related decay rate <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mi mathvariant="normal">Γ</e:mi><e:mo>=</e:mo><e:mn>2.86</e:mn><e:mrow><e:mo>(</e:mo><e:mn>8</e:mn><e:mo>)</e:mo></e:mrow><e:mo>×</e:mo><e:msup><e:mn>10</e:mn><e:mn>7</e:mn></e:msup></e:mrow></e:math> <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:msup><g:mtext>s</g:mtext><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup></g:math> are of relevance to the laser cooling of RaF via the optically closed <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mi>A</h:mi><h:mspace width="0.16em"/><h:mmultiscripts><h:mi mathvariant="normal">Π</h:mi><h:mrow><h:mn>1</h:mn><h:mo>/</h:mo><h:mn>2</h:mn></h:mrow><h:none/><h:mprescripts/><h:none/><h:mn>2</h:mn></h:mmultiscripts><h:mo>←</h:mo><h:mi>X</h:mi><h:mspace width="0.16em"/><h:mmultiscripts><h:mi mathvariant="normal">Σ</h:mi><h:mrow><h:mn>1</h:mn><h:mo>/</h:mo><h:mn>2</h:mn></h:mrow><h:none/><h:mprescripts/><h:none/><h:mn>2</h:mn></h:mmultiscripts></h:mrow></h:math> transition, which makes the molecule a promising probe to search for new physics. RaF is found to have a comparable photon-scattering rate to homoelectronic laser-coolable molecules. Owing to its highly diagonal Franck-Condon matrix, it is expected to scatter an order of magnitude more photons than other molecules when using just three cooling lasers, before it decays to a dark state. The lifetime measurement in RaF is benchmarked by measuring the lifetime of the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:mrow><m:mn>8</m:mn><m:msub><m:mi>P</m:mi><m:mrow><m:mn>3</m:mn><m:mo>/</m:mo><m:mn>2</m:mn></m:mrow></m:msub></m:mrow></m:math> state in Fr to be 83(3) ns, in agreement with literature. Published by the American Physical Society 2024