Positronium is a short-lived ( 10^ -9 ~s) bound state of an...

Positronium is a short-lived $\left(\approx 10^{-9} \mathrm{~s}\right)$ bound state of an electron and a positron (a positively charged particle with mass and charge equal (in magnitude) to an electron) revolving round their common centre of mass. If $\mathrm{E}_0, \mathrm{v}_0$ and $\mathrm{a}_0$ are respectively the ground state energy, the orbital speed of electron in first orbit and the radius of the first ( $n=1$ ) Bohr orbit for Hydrogen atom, the corresponding quantities $\mathrm{E}, \mathrm{v}$ and a for the positronium are