DR rate coefficient measurements using stored beams of H₃⁺ and its isotopomers

In studies of the rate coefficient of the dissociative recombination of H₃⁺ and its isotopomers, the rovibrational excitation of the molecular ions was found to play an important role, in particular when employing the technique of heavy-ion storage rings. The dependence of the DR rate on rotational excitation was investigated in recent experiments at the Test Storage Ring TSR in Heidelberg through time-resolved measurements on D₂H⁺ and H₃⁺ over long storage times. For both molecules, an influence of rotational excitation on the DR rate was observed. The level of excitation in turn was found to be dominated by radiative coupling to the surrounding 300 K background for D₂H⁺. In the case of H₃⁺, a strong influence of electron collisions on the excitation level was found, whereas an additional influence of collisions with residual gas in the storage ring cannot be excluded