The hydrogen atom in a strong microwave field

Using an apparatus of the type shown in Fig. 7.1, Bayfield and Koch (1974) conducted an ionization experiment with hydrogen Rydberg atoms that were prepared in the band 63 tiq 69 and exposed to electromagnetic radiation of three different frequencies Wj = 2nfi, with fi = 30 MHz, 

Both definitions are natural since wq turns out to be the ratio of the microwave frequency w and the Kepler firequency H of the Rydberg electron, and Sq is the ratio of the microwave field strength and the field strength experienced by an electron in the noth Bohr orbit of the hydrogen atom. Motivated by the above discussion we have redrawn the results obtained by Bayfield and Koch (1974) and present them in Fig. 7.2 as an ionization signal (in arbitrary units) versus the scaled field strength defined in (7.1.3). For no in (7.1.3) we chose no = 66, the centroid of the band of Rydberg states present in the atomic beam. 

It is demonstrated in the following section that quantum calculations in large basis sets are able to reproduce qualitatively the threshold behaviour of the ionization curves. This demonstrates that there is no mystery beyond quantum mechanics hidden in the experimental results. But although numerical quantum calculations reproduce the experimental results adequately, they are limited in that they do not provide us with any insight into the physical mechanisms responsible for the occurrence 

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Bayfield and Koch (1974) provided the first experimental results on a manifestly quantum, but classically chaotic, system hydrogen Rydberg atoms in a strong microwave field. Both pioneers, Bayfield at Pittsburgh and Koch at Stony Brook, continue to contribute actively to the investigation of time dependent chaos in Rydberg atoms. 

In Section 11.1 we discuss recent advances in quantum chaology, i.e. the semiclassical basis for the analysis of atomic and molecular spectra in the classically chaotic regime. In Section 11.2 we discuss some recent results in type II quantum chaos within the framework of the dynamic Born-Oppenheimer approximation. Recent experimental and theoretical results of the hydrogen atom in strong microwave and magnetic fields are presented in Sections 11.3 and 11.4, respectively. We conclude this chapter with a brief review of the current status of research on chaos in the helium atom. 

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