  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.
