2005MNRAS.363..897O

Using the `son of ISAAC' (Infrared Spectrometer And Array Camera) imager at the European Southern Observatory New Technology Telescope and the near-infrared spectrographs on Keck II, we have obtained J, K images and echelle spectra covering the range 1.5-1.8µm for the intermediate metallicity bulge globular clusters NGC 6539 and UKS 1. We find [Fe/H]=-0.76 and -0.78, respectively, and an average α-enhancement of ~+0.44 and ~+0.31 dex, consistent with previous measurements of metal-rich bulge clusters, and favouring the scenario of rapid chemical enrichment. We also measure very low ¹²C/¹³C ~ 4.5±1 isotopic ratios in both clusters, suggesting that extra-mixing mechanisms due to cool bottom processing are at work during evolution along the red giant branch. Finally, we measure accurate radial velocities of <v_r≥+31±4 and <v_r≥+57±6 km/s and velocity dispersions of ~8 and ~11 km/s for NGC 6539 and UKS 1, respectively,