Valence-Rydberg

The extensive calculations of Serrano-Andres et al [31] have shown a spurious valence-Rydberg mixing in the CASSCF wave functions when valence (7t,7r )and Rydberg orbitals are optimized all together in a state average calculation it was shown that these orbitals loose their diffuse character and instead tend to provide an extra correlation to valence orbitals. To avoid such interaction, the orbitals used for the Cl treatment of the electronic spectrum were obtained by a two step procedure ... 

XAS, on the other hand has a core-excited final state for which the effect of the core-hole must be taken into account. To obtain the full spectrum, i.e., valence, Rydberg and continuum excitations, we use the Slater transition-state approach [22,23] with a half-occupied core-hole. This provides a balanced description of both initial and final states allowing the same orbitals to be used to describe both initial and final states and all transitions are obtained in one calculation [23,24]. Details of the computational procedure can be found in the original papers as referenced in the following sections. In the present chapter, the focus is on the surface chemical bond and the spectra, measured or calculated, will mainly be used to obtain the required information on the electronic structure. 

In this chapter we have implicitly assumed the Rydberg atom to be a one electron-atom. In the perturbed Rydberg series of, for example, alkaline earth atoms, Rydberg states can have mixed valence-Rydberg character. In such states the black body effects are reduced by a factor equal to the fractional Rydberg character.14... 

Einstein coefficients for the Vegard-Kaplan system in a logarithmic scale. Valence + Rydberg CAS (CAS-2, solid line), experimental data (dashed line) [89]. Prom ref. [26]. 

Atom N Charge Core Valence Rydberg Total... 

The dependence of the Fermi-sea on symmetry, spin, and the parameters of the Hamiltonian. Valence-Rydberg state mixing... 

In the early 1970s, when it had been recognized that experiments of beam-foil specfroscopy could produce lifetimes for many types of atomic transitions, we carried out a number of computations and analyses of transifion probabilities in atoms, with and without heavy valence-Rydberg state mixing. As we wrote in Ref. [26b], fhaf work revealed that (non int) corresponds to correlation vectors with small coefficients which are reasonably well decoupled from T and (int). This implies A) Their direct contribution to (, D /) is very small. I.e., the last three terms of eq. (12) are negligible because of the small... 

Due to economy, I give only two numerical examples of such calculations (see Refs. [20, 22, 26b, 45] and references therein). The first concerns the oscillator strengths (/ - values) of the valence-Rydberg state spec-... 

Table 2.3 Oscillator strengths (length fi, velocity, fy) for the ls 2s2pV° - valence-Rydberg state spectrum of Be. Comparison of the FOTOS results [26b] with those from large-scale MCHF calculations [48a] and with experiment [48b, 48c]...

The OH applications discussed here involve transitions between valence states. The application of the SA-CASSCF/MRCI approach to valence-Rydberg transitions poses additional problems. The requirement of adding diffuse orbitals to the one-particle basis set to describe the Rydberg character is well known, so we focus on the requirements for the n-particle treatment. An excellent system for such a calibration is the AlH molecule, which can be treated very well as a four-electron system, simile L-M intershell correlation introduces only a small bond contraction. The FCI study of AlH included the and A H valence states and the Rydberg state (see... 

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