Terms Rydberg orbitals

The space spanning the CSFs used in the calculation is presented in Table 1. Orbitals are distributed into several sets, and ordered by symmetry. They are denoted in terms of loealized orbitals (Fig. 1) in order to emphasize their "ehemieal" signifieanee Table 1 presents the various distributions of the correlated eleetrons into these sets, with R standing for Rydberg orbitals or Rydberg states. 

Figure 9.1. Energy level diagram for hydrogen molecule, H2, and separated atoms H R = 00) and He R = 0). R = the Rydberg constant = 13.6057 eV = 0.5 a.u. (atomic unit of energy). Value from ionization potential of He (Is 2p P). Value from ionization potential of H2. The experimental ionization potentials are quite precise but for systems containing more than one electron their interpretation in terms of orbital energies is an approximation.

Table II, which is adapted from a previous description (Nenner 1987 Nenner et al. 1988), presents some of the electronic relaxation processes associated with the decay of a core hole. In these equations, c represents a core orbital, v an occupied valence orbital, u an unoccupied valence or Rydberg orbital, and s represents a shape resonance orbital. The term orbital is used simply to mean a one-electron wavefunction. An electron in a continuum orbital free from the influence of the molecular potential is represented as e .

For valence states of nonhydride molecules, there is no reason to expect that the generalized pure precession approximation should be valid. In contrast, Rydberg orbitals, because of their large size and nonbonding, single-center, near-spherical, atomic-like character, are almost invariably well-described by the pure precession picture in terms of nl-complexes. 

When aos are eombined to form mos, eore, bonding, nonbonding, antibonding, and Rydberg moleeular orbitals ean result. The mos (j) are usually expressed in terms of the eonstituent atomie orbitals Xa iii the linear-eombination-of-atomie-orbital-moleeular-orbital (LCAO-MO) manner ... 

The existence of outsized hydrogen atoms was inferred early on from the observation that 33 terms of the Balmer series could be observed in stellar spectra, compared to only 12 in the laboratory [58]. More recently [59] Rydberg atoms have been produced by exciting an atomic beam with laser light. When the outer electron of an atom is excited into a very high energy level, it enters a spatially extended orbital which is far outside the orbitals... 

Thus, these orbitals can be used to represent exactly any property of the system in localized terms. The NAOs divide naturally into a leading high-occupancy set (the natural minimal basis ) and a residual low-occupancy set (the natural Rydberg basis ), where the occupancies of the latter orbitals are usually quite negligible for chemical purposes. Thus, even if the underlying variational basis set is of high dimensionality (6-311++G for the applications of this book), a perturbative analysis couched in NAO terms has the simplicity of an elementary minimal-basis treatment without appreciable loss of chemical accuracy. 

Recent results show that even after the annihilation of periodic orbits at a bifurcation there remain traces of the annihilated periodic orbits in the quantum amplitudes [50]. These so-called ghost periodic orbits have been interpreted in terms of the complex periodic orbits created when the corresponding real periodic orbits are annihilated. Such phenomena have been experimentally observed for Rydberg atoms in a magnetic field [11,51]. We shall show below that such phenomena are also important in intramolecular and dissociation dynamics. 

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