Vibrational cooling of D2+ in an ion storage ring as revealed by dissociative recombination measurements

It is demonstrated that a substantial degree of vibrational cooling of an infrared inactive molecule can be achieved by means of storage in an ion cooler ring. The cross section for dissociative recombination of D2+ has been measured in the storage ring CRYRING using 6 MeV amu-1 ions and variable storage times prior to data taking. By using a simple model for describing the recombination process, it is inferred that 68% of the D2+ ions remaining in the ring after 22.5 s populate nu =0. It is proposed that the removal of vibrational excitation contained in the ions injected into the ring is due to collisions in the rest gas. The rate coefficient measured for 22.5 s storage time, alpha (T=300 K)=2.3*10-8 cm3 s-1 is in very good agreement with theoretical predictions.