Rydberg electron frequencies

H. J. Neusser In relation to the comment by Prof. Yamanouchi, we should notice that an efficient interaction of the Rydberg electron with vibrations of the core is expected for small vibrational frequencies. Benzene as a rigid molecule has relatively large vibrational frequencies of more than 300 cm"1. An efficient coupling is expected for van der Waals complexes (e.g., the benzene-Ar complex) with low van der Waals vibrational frequencies of about 30 cm 1. 

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. 

The analytical computation of critical ionization fields starts with an analysis of the widths of resonances in the classical phase space. Resonances occur whenever the ratio of the external driving frequency u and the unperturbed Kepler frequency Cl of the Rydberg electron is rational, i.e. 

This picture is that described by the BO approximation. Of course, one should expect large corrections to such a model for electronic states in which loosely held electrons exist. For example, in molecular Rydberg states and in anions, where the outer valence electrons are bound by a fraction of an electron volt, the natural orbit frequencies of these electrons are not much faster (if at all) than vibrational frequencies. In such cases, significant breakdown of the BO picture is to be expected. 

Figure 12. Level scheme of the rotationally resolved high-n Rydberg experiment. A first narrow-band laser pulse excites the molecule from the electronic ground state So into a single rotational state in the electronically excited S state. The frequency of the second laser pulse is scanned to obtain the rotationally resolved Rydberg spectrum shown in Fig. 13.

Another metrological application of simple atoms is the determination of values of the fundamental physical constants. In particular, the use of the new frequency chain for the hydrogen and deuterium lines [6] provided an improvement of a value of the Rydberg constant (Roc)- But that is not the only the constant determined with help of simple atoms. A recent experiment on g factor of a bound electron [27,11] has given a value of the proton-to-electron mass ratio. This value now becomes very important because of the use of photon-recoil spectroscopy for the determination of the fine structure constant [41] (see also [8])-... 

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