Oscillations, Waves, and Interactions - GWDG

12 M. R. Schroeder, D. Guicking and U. Kaatze
of rapidly changing deep objects with frame rates up to 300 000 s −1 , corresponding
to a 3-µs time interval between two pictures [112,113]. Such advanced holographic
methods were used to investigate time-dependent cavitation phenomena, such as
period-doubled and chaotic bubble oscillations [114].
9 Nonlinear dynamics
Much of classical physics is based on linear laws. But in recent decades nonlinearity
has come to the fore. With Werner Lauterborn and his coworkers nonlinear dynamics
has been added to the research repertoire at the Dritte Physikalische Institut [98,115].
In particular Lauterborn studied the nonlinear oscillations of cavitation gas bubbles
in liquids which show nonlinear resonances [116], period-doubling bifurcations,
and chaotic dynamics [117,118]. Soon thereafter the Lauterborn group investigated
chaotic dynamics and bifurcations in periodically excited nonlinear oscillators [119–
121] and coupled oscillators [122,123]. Later Lauterborn and others shed light on the
nonlinear dynamics of lasers [124–126] and nonlinear waves and solitons [127,128]. In
seperate investigations, Parlitz and colleagues studied the synchronisation properties
of chaotic systems, methods for time series analyses and predictions, and also control
of chaos. Part of these investigations is described in more detail in the article by
Ulrich Parlitz [99] of this book.
10 Complex liquids
In the years before the invention of the laser in 1960, microwaves were used in demonstration
experiments [129] requiring coherent electromagnetic signals, and in diffraction
studies [130,131]. At that time much work was devoted to the development
of microwave techniques, including transmission lines [132], antennas [133], and absorbers
[134–137]. This applied research soon induced interest in the principles of
molecular systems. Electromagnetic waves were used to investigate aspects of ferroelectricity
[132,138–141] and ferromagnetism [142,143] and to perform dielectric studies
of the molecular behaviour of liquids [144]. The application to molecular physics
was greatly facilitated by an extensive collection of radio frequency and microwave
devices at the institute and, thanks to the excellent support by the electronics and
precision engineering workshops, the Dritte became soon well known for its sophisticated
broadband measuring methods in liquid research. Later ultrasonic attenuation
spectrometry was extended to cover a very broad frequency range [145–147].
Additional methods, such as shear wave spectrometry [148] and dynamic light scattering
[149] were also used.
Peter Debye, professor for theoretical and experimental physics at Göttingen from
1914 to 1920, was the first to illuminate the molecular aspects of the interactions
of electromagnetic waves with materials. A significant step towards dielectric spectroscopy
of liquids was Reinhard Pottel’s broadband study of 2:2 valent electrolyte
solutions in which he verified the existence of dipolar ion complex structures [150],
as had been suggested by Günter Kurtze, Konrad Tamm and Manfred Eigen on the
basis of ultrasonic spectroscopy [146,151,152].