Analytical study of the thermal induced oscillations known as heartbeats

摘要

A laser beam traveling horizontally at a short distance below the free surface of an absorbing solution exhibits various oscillatory stares (periodic, quasiperiodic, and chaotic) which depend on both the buoyancy (Archimedes force) and the thermal coefficient of the surface tension (Marangoni effect). The beam oscillations have been called "heartbeats." In this work, the heartbeats were produced by pumping 1-(2-pyridylazo)-2-naphthol (PAN) solutions in silicone oil with an Ar+ continuous-wave laser beam. The relationships between PAN concentration and the other parameters that control the oscillatory behavior were studied. The frequency of the oscillations sensitively varied with small PAN concentration changes, but a threshold set by a combination of absorbance, laser power, and distance from the beam to the free surface was required to obtain the oscillations. (C) 1998 Academic Press. [References: 11]