CH + in the Interstellar Medium

This paper describes observations of interstellar CH(+) along the lines of sight to O and B stars with E(B-V)s up to +1.13. Along some lines of sight with strong detections of CH(+), we find distinct radial velocity shifts between the CH(+) lines and other neutral species, such as Ca I and CH. The shifts are small but are predicted by shock models of CH(+) formation in which the shock is inclined with respect to the observer. We have also found no column densities exceeding approximately 10^13.8/sq cm. When these data are examined along with the other CH(+) data collected from the literature, the previously seen tendency of CH(+) column density to increase with E(B-V) does not continue beyond reddenings of about +0.6. These findings offer support to the shock model of CH(+) formation for at least some lines of sight.