A new closed gas-phase system with complex oscillatory behaviour is reported. Employing the pulsed cavity ring-down technique, the absorption of static naphthalene vapour buffered with a noble gas at room temperature was measured as a function of time at 650 nm after UV multi-photon laser photolysis at 308 nm. The absorption dynamics of the static (unstirred) system exhibits extraordinary periodic and complex oscillations with periods ranging from seconds to many minutes, persisting for up to 4 h. Depending on the buffer gas pressure, several types of dynamical responses can be generated.A new closed gas-phase system with complex oscillatory behaviour is reported. Employing the pulsed cavity ring-down technique, the absorption of static naphthalene vapour buffered with a noble gas at room temperature was measured as a function of time at 650 nm after UV multi-photon laser photolysis at 308 nm. The absorption dynamics of the static (unstirred) system exhibits extraordinary periodic and complex oscillations with periods ranging from seconds to many minutes, persisting for up to 4 h. Depending on the buffer gas pressure, several types of dynamical responses can be generated.