To investigate how the initial charge state affects the transmission of 4MeV C+ and C4+ ion beams through a channel, we measured the transmission probability and kinetic energy of atoms and ions that pass through a cylindrical channel in glass, such as a narrow gap between a cylindrical convex glass surface and a cylindrical concave glass surface. Kinetic energy distributions were measured at three typical observation angles f with the cylindrical glass channel tilted at angles phi= - 3, - 2, - 1, 0, 1, 2, and 3(circle) with respect to the incident ion beam. The ion beam is guided in both initial charge states; that is, the transmission maintains the initial kinetic energy at tilt angles greater than the geometric limit. However, no marked difference in transmission appears between the two initial charge states. (C) 2017 The Japan Society of Applied Physics