Oscillations, Waves, and Interactions - GWDG

(a)
(b)
The single bubble – a hot microlaboratory 161
(c)
Figure 25. Luminescence light output
(top) and longitudinal- and transversesection
pseudo-streak images (bottom)
of femtosecond-laser-generated bubbles
(44 kHz, 159 kPa) as a function of seeding
phase ϕs. (a) At ϕs =184 ◦ luminescence
appears but is still weak, (b)
at ϕs =192 ◦ it reaches a maximum and
(c) at ϕs =201 ◦ diminishes again. Note
that luminescence data and each vertical
slice of the streak images have been
obtained from different bubbles generated
at the same conditions. For details,
see Ref. [27].
as mentioned before, the non-driven bubbles do not emit light, weak luminescence of
the driven bubbles could be detected in two small intervals of the seeding phase. The
first interval around ϕs = 192 ◦ is shown in the figure and nearly coincides with the
region of maximum bubble expansion seen in Fig. 23. Closer analysis of the bubble
shape reveals that light emission in this regime appears to depend sensitively on the
roundness of the bubble immediately before collapse. The same is true for the second
phase interval around ϕ =331 ◦ where light emission is observed upon the delayed,
strong collapse (Fig. 26).