Measurements of the 23S1-2(3)PJ (J=0,1,2) fine-structure splittings in positronium.

Abstract

The ${2}^{3}$${\mathrm{S}}_{1}$\ensuremath{\rightarrow}${2}^{3}$${\mathrm{P}}_{1}$ and ${2}^{3}$${\mathrm{S}}_{1}$\ensuremath{\rightarrow}${2}^{3}$${\mathrm{P}}_{0}$ transition frequencies (${\ensuremath{\nu}}_{1}$ and ${\ensuremath{\nu}}_{0}$, respectively) in positronium have been measured for the first time and an improved measurement of the ${2}^{3}$${\mathrm{S}}_{1}$\ensuremath{\rightarrow}${2}^{3}$${\mathrm{P}}_{2}$ transition frequency (${\ensuremath{\nu}}_{2}$) has been made. The results ${\ensuremath{\nu}}_{0}$=18504.1\ifmmode\pm\else\textpm\fi{}10.0\ifmmode\pm\else\textpm\fi{}1.7 MHz, ${\ensuremath{\nu}}_{1}$=13001.3\ifmmode\pm\else\textpm\fi{}3.9\ifmmode\pm\else\textpm\fi{}0.9 MHz, and ${\ensuremath{\nu}}_{2}$=8619.6\ifmmode\pm\else\textpm\fi{}2.7\ifmmode\pm\else\textpm\fi{}0.9 MHz are in reasonable agreement with the predictions of quantum electrodynamics which are, to order ${\mathrm{\ensuremath{\alpha}}}^{3}$Ry, ${\ensuremath{\nu}}_{0}$(${\mathrm{\ensuremath{\alpha}}}^{3}$)=18496.1 MHz, ${\ensuremath{\nu}}_{1}$(${\mathrm{\ensuremath{\alpha}}}^{3}$)=13010.9 MHz, and ${\ensuremath{\nu}}_{2}$(${\mathrm{\ensuremath{\alpha}}}^{3}$)=8625.2 MHz. More precise measurements are planned to test the, as yet uncalculated, order ${\mathrm{\ensuremath{\alpha}}}^{4}$ Ry corrections.