The interaction of slow iodine highly charged ions (HCIs), Iq+, with a hydrogen-terminated Si(1 1 1)-(1 x 1) surface was investigated for a wide range of q from 17 to 53 (fully stripped ion). The coincidence measurement for secondary ion emission reveals that correlated sputtering is enhanced toward higher q, that is, while Si+ sputtering is anti-correlated with H+, multiple H+ are simultaneously emitted. The direct observation of the HCI-bombarded surface with a scanning tunneling microscope supports the result of the multiple hydrogen emission. These results are discussed in consideration of the strong Coulomb interaction of incident HCIs with the surface and subsurface atoms. (C) 2010 Elsevier B.V. All rights reserved.