Our calculations show that during the collapse of the bubble, a shock wave is generated that compresses and heats the contents of the bubble. More heating occurs at the center of the bubble than at its boundary because the shock wave's strength increases as it approaches the bubble's center. The final 50 ps of the calculated collapse of an argon bubble. The figure shows our calculated results for a collapsing argon bubble. Five snapshots of the final 50 ps of the collapse are shown, during which the radius of the bubble decreases from 0.45 to 0.43 microns.
Time is referenced to the instant when the shock wave reaches the center of the bubble.
At 0 ps, the shock reaches the center of the bubble. The solid black region in the figure shows where the bubble is optically thick. At 15 ps, the shock has reflected from the center of the bubble and is moving outward, but the gas outside the shock is still moving towards that bubble's center, compressing, and heating. Consequently, the emitting halo is slightly larger and the emitted visible optical power is at its peak value. At 25 ps, the light emitting halo is even larger, but the bubble has cooled, so that the emitted visible optical power has decreased to one-half its peak value.