positronium (Ps) atoms entered a waveguide whose internal surfaces were lined with
smoked magnesium oxide (MgO) powder. The waveguide was built such that time-delayed
microwave radiation pulses, tuned to drive $2\,^{3}\mathrm {S} _ {1}\rightarrow
2\,^{3}\mathrm {P} _ {2} $ transitions, could be applied to the Ps ensemble. The lifetime of
$2\,^{3}\mathrm {S} _ {1} $ atoms was measured using time-delayed microwave induced …