Rydberg state

Within the last ten years the spectroscopic features of highly excited atoms, called Rydberg atoms, increasingly attracted the interest of many scientists. The general physics of Rydberg atoms which exhibits numerous peculiarities has been reviewed in several articles (see, e.g.. Ref. 174-178), and in a recent book, and therefore will not be discussed here in detail. Also, Chapters 11 and 16 of Progress in Atomic Spectroscopy, Parts A and B, deal with Rydberg atoms. 

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The measurements were extended to two-photon and three-photon absorption related to d-g and d-h transitions, respectively, in the n = 13-17 states of sodium. In the case of the three-photon transitions, a microwave frequency was swept while an rf frequency was fixed, and two rf photons and one microwave photon were absorbed. The detection scheme was the same as in Ref. 192. The measurements provided accurate quantum defect values and revealed hydrogenic fine structures for I 2. 

Similar measurements of d-f and d-g intervals in lithium Rydberg states by Cooke et yielded fine structure intervals in accordance with the hydrogenic theory. Ruff and co-workers measured n = 15-17 f-g intervals in Cs and determined values for the effective Cs dipole and quadrupole polarizabilities. To reach the Rydberg levels the first laser excited atoms from the 6si/2 ground state to the lp-i/2 state, from which they cascaded to the 5ds/2 level. The second laser then induced the 5ds/2-16/7/2 transition. This excitation technique was first used by Lundberg and Svanberg for lifetime measurements.  

Several autoionization features observed In a plot of the photoionization yield of PHJ from PH2 (obtained from the PH3 + H reaction) between 1259 and 1113 A (9.85 to 11.1 eV) probably are members of Rydberg series converging on the excited states a Bi and A B of the PHJ ion (see p. 95). The bending vibration apparently leads to a vibrational structure (for a more detailed discussion, see the original paper) [55]. 

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Three-photon absorption has also been observed by multiphoton ionization, giving Rydberg states of atoms or molecules [36]. Such states usually require vacuum ultraviolet teclmiques for one-photon spectra, but can be done with a visible or near-ultraviolet laser by tluee-photon absorption. 

Sandorfy C (ed) 1999 The Role of Rydberg States in Spectroscopy and Photochemistry (London Kluwer Academic)... 

Merkt F 1997 Molecules in high Rydberg states Ann. Rev. Phys. Chem. 48 675-709... 

This pieture is that deseribed by the BO approximation. Of eourse, one should expeet large eorreetions to sueh a model for eleetronie states in whieh loosely held eleetrons exist. For example, in moleeular Rydberg states and in anions, where the outer valenee eleetrons are bound by a fraetion of an eleetron volt, the natural orbit frequeneies of these eleetrons are not mueh faster (if at all) than vibrational frequeneies. In sueh eases, signifieant breakdown of the BO pieture is to be expeeted. 

The calculation done without including diffuse functions in the basis set fails to find three of the lower excited states. It does still compute excitation energies for six excited states, but the other three states are higher in energy than the 8.75 eV state, and do not correspond to the missing states observed by experiment. The three missing states are Rydberg states, observable via multiphoton ionization experiments. 

Blasse G (1976) The Influence of Charge-Transfer and Rydberg States on the Luminescence Properties of Lanthanides and Actinides. 26 43-79 Blasse G (1980) The Luminescence of Closed-Shell Transition Metal-Complexes. New Developments. 42 1-41... 

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. 

We emphasize that the Rydberg states are included in the variational MCSCF treatment in order not to be undercorrelated relative to the valence states [48,49], Furthermore, it is seen that all the previous distributions are coupled to diexcitations from the oco to the oco orbital that way, we account for the non-dynamical repolarization of the polar acobond in a GVB-like approach. 

The orbitals employed to build the reference configurations were taken from atomic SCF calculations for the appropriate states of B. B, . H. and. Hj, only for the valence orbitals of the Rydberg states, BPS.3sl Hf Sl and Bf P.dol Hf Sl. we have... 

To account for Rydberg states, the MCSCF/SD set of orbitals was extended by atomic... 

Because Rydberg states are peculiar states with a core resembling the positive ion and one electron in a diffuse orbital, the A] Rydberg states have been recalculated with orbitals optimized for the ion, with the same MCSCF/SD expansion. An improvement of 0.2 eV is obtained, arguing for the use of this type of MOs for Rydberg A, states. 

Our best estimation for the vertical excitation energies for states of A, symmetry are reported in Table 12. They correspond to a ground state calculated at CI( 6) level using orbitals optimized for the neutral molecule with the MCSCF/SD expansion, and excited Rydberg states calculated at the level using orbitals optimized for the positive ion... 

Vertical excitation energies to states of B symmetry, calculated at the level using the orbitals optimized for the neutral molecule with the MCSCF/6422 expansion, are reported Table 12. The I Bi valence state and 2 B (3p) Rydberg state of C3H2 are respectively 5.2 eV and 7.5 eV above the ground state with large transition moments of... 

Figure 7. Potential energy diagram for HI, showing the two lowest ionization states (2n3//2 and 2 IT j, ) coupled to a neutral dissociative continuum (3Ao) at the three-photon (3

Uracil has eight n orbitals and two lone pair no orbitals on the two oxygen atoms. The lowest excited states, if we neglect Rydberg states, originate from excitations from these valence orbitals. Figure 11-3 shows the orbitals mainly participating in the first four excited states. The excited states of uracil have been studied theoretically... 

Oscillator strengths are given in parenthesis. a nit state. b 7171 state. c Rydberg state. 

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