Fine structure in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math>decay of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">Po</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>188</mml:mn><mml:mo>,</mml:mo><mml:mn>192</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>

The $\ensuremath{\alpha}$ decay of $^{188,192}\mathrm{Po}$ has been reexamined in order to probe the ${0}^{+}$ states in the daughter nuclei $^{184,188}\mathrm{Pb}$ that can be associated with coexisting spherical, oblate, and∕or prolate configurations. Improved values were measured for the excitation energy and the feeding $\ensuremath{\alpha}$-decay intensity of the ${0}_{2}^{+}$ state in $^{184,188}\mathrm{Pb}$ and conflicting results on the ${0}_{3}^{+}$ state in $^{188}\mathrm{Pb}$ were clarified. All known cases of fine structure in the $\ensuremath{\alpha}$ decay of the even-even Po nuclei are reviewed. The reduced $\ensuremath{\alpha}$-decay width systematics combined with potential-energy-surface calculations confirm the onset of deformation in the ground state of the polonium nuclei around the neutron midshell. An isomeric state with a half-life of $580(100)\text{ns}$ has been identified in $^{192}\mathrm{Po}$.

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