The time evolution of ground‐ and metastable‐state copper atom concentrations and the laser energy in a bust‐mode CuBr laser were measured as a function of temperature, buffer gas species, and repetition rate within the burst. The concentrations were measured by monitoring the absorption of the 244.2‐ and 510.6‐nm atomic copper lines. The optimum time separations of the electrical pulses within the burst were found to be 80 and 235 &mgr; for helium and argon buffer gases, respectively. A correlation was found between the time dependences of the laser energy and ground‐state density within the burst. Accumulation was found to occur in the copper atom ground state but not in the metastable2D5/2level.