PHOTORECOMBINATION OF TI4- SEARCH FOR INTERFERENCE EFFECTS, RECOMBINATION AT LOW ENERGIES AND RATE COEFFICIENT IN PLASMAS( IONS )

in the search for interference between radiative and dielectronic reco mbination (RR and DR), absolute recombination rate coefficients for Ar -like Ti4+ ions have been measured at the Heidelberg Test Storage Ring in the centre-of-mass energy range 0-80 eV. The dominant recombinatio n channels beside RR is Delta n = 0 DR via the formation of Ti3+ (3s(2 ) 3p(5) 3d P-1 nl) and Ti3+(3s(2)3p(5)3d P-3 nl) intermediate doubly e xcited states. The Delta n = 0 Ti4+ DR rate coefficient in plasmas is inferred from this measurement. it is about a factor of 3 lower than t he previously available result based on a semi-empirical calculation. Asymmetric lineshapes due to quantum mechanical interference as recent ly predicted theoretically for isoelectronic SC3+ ions have not been o bserved. The broad Ti3+(3s(2)3p(5)3d(2) F-2 DR resonance expected on t he basis of multiconfiguration Hartree-Fock calculations at 3.0 eV wit h a width of 1.3 eV appears to be shifted towards zero centre-of-mass energy where an unexplained recombination rate enhancement of a factor of 2 beyond the sum of RR and DR rates is observed.