Forbidden transition properties in the ground-state configurations of singly ionized noble gas atoms for stellar and interstellar media

High-accuracy calculations of the forbidden transition amplitudes for the np²P<inf>1/2</inf> → np²P<inf>3/2</inf> transitions with the ground-state principal quantum number n in singly charged inert gas atoms, which are of astrophysical interest, have been carried out using sophisticated relativistic many-body methods. Using these amplitudes, the line strengths, oscillator strengths and transition probabilities of the above transitions and lifetimes of the np²P<inf>1/2</inf> states are estimated precisely. Most of these transition wavelengths lie in the infrared region, while the corresponding Rn II line is the optical one, and they can be observed in the stellar and interstellar media, where the abundances of these ions have already been identified. The above forbidden transitions can also be very useful for astrophysical plasma diagnostics and can guide experiments to measure the lifetimes of the above np²P<inf>1/2</inf> states.