[en] The transmission of 18-keV O^- ions through Al₂O₃ nanocapillaries with 50 nm in diameter and 12 μm in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV O^-) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (O^-, O⁰, and O⁺) decreased when the tilt angle increased. In transmitted particles, the fraction of O^- declined but that of O⁰ and O⁺ ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.