In an ordianary atom, as a first approximation, the motion of the nucleus can be ignored. In a positronium atom a positronreplaces the proton of hydrogen atom. The electron and positron masses are equal and , therefore , the motion of the positron cannot be ignored. One must consider the motion of both electron and positron about their center of mass. A detailed analyasis shows that formulae of Bohr's model apply to positronium atom provided that we replace `m_(e)` by what is known reduced mass is `m_(e)//2`.
If the Rydberg constant for hydrogen atom is `R` , then the Rydberg constant for positronium atom is

Options

A. `2 R`
B. `R`
C. ` R//2`
D. `4 R`

Answer

C

Explanation

`R prop m`