Long optical pulses have been generated in a XeCl excimer laser by using a simple capacitor‐transfer discharge circuit consisting of storage capacitors charged at 26 kV and discharged through the electrodes, tightly coupled to the variable small peaking capacitors. By adjusting the [HCl] concentration and capacitance ratios, the typical pulse duration (20 ns) is stretched up to 150 ns (full width at half‐maximum). The transfer behaviors of the pulse duration from short pulse to long pulse are presented and analyzed extensively by measuring the discharge voltage profile, output energy, overall efficiency, optical waveform, and pulse duration, as functions of [HCl] concentration and capacitance ratios. ©1994 American Institute of Physics.