Variations in Sonoluminescence Flash Timing

Since the first experimental results were published in the 1990s, it has been believed that the sonoluminescence flash always occurs no more than a few nanoseconds before the minimum radius of a collapsing bubble. A concurrent belief has been that the period between sonoluminescence flashes is steady on the order of a few nanoseconds, and that sonoluminescence flashes occur with a "clock-like" regularity. To the contrary, data presented here show that the sonoluminescence flash can occur hundreds of nanoseconds before the minimum radius and that the sonoluminescence flash-to-flash period can vary on the order of hundreds of nanoseconds. These new findings may require a reexamination of the physics of sonoluminescence.