Quantum Chaos Observed in Photoionization

Using a modern variant of the experiments at the dawn of quantum physics that probed the photoelectric effect, scientists at Max Planck Institut für Quantenoptik in Garching, Germany, have found that photoionized rubidium-85 atoms simultaneously exposed to electric and magnetic fields display quantum chaotic scattering. The work, which whey reported in the Nov. 4 issue of Physical Review Letters, gives weight to the hypothesis that a chaotic phenomenon observed in nuclear reactions also holds at the atomic level.

In their setup, the scientists used a 780-nm laser diode and a 480-nm ring dye laser to photoexcite a beam of ⁸⁵Rb atoms exposed to crossed magnetic and electric fields. The particular ionization regime — slow or fast — of the atoms in the crossed fields determined the position of their electrons at the detector region of the apparatus.

The investigators confirmed that the detected photoelectron current displayed so-called Ericson fluctuations known from nuclear physics. They also found that they could change the degree of quantum chaotic scattering by adjusting the relative strength of the electric and magnetic fields, confirming the predictions of another research team.