The transition between Mach reflection (MR) and regular reflection (RR) of gaseous detonations in argon-diluted stoichiometric hydrogen–oxygen was investigated experimentally using a wedge with a concave–convex surface. The continuous MR triple-point trajectory was recorded using the smoked foil technique, from which the transition angles for \({\textrm{MR}}\leftrightarrow {\textrm{RR}}\) transitions could be determined. Similar to the reflection of a non-reacting shock wave, the non-stationary hysteresis phenomenon was found for detonation reflection, i.e., the \({\textrm{MR}}\rightarrow {\textrm{RR}}\) transition angle was much larger than that for \({\textrm{RR}} \rightarrow {\textrm{MR}}\) transition. In addition, the \({\textrm{RR}} \rightarrow {\textrm{MR}}\) transition angle on the convex surface was smaller than that for detonation reflection over a single half-cylinder. This is opposite to what is found for non-reacting shock wave reflection.
