Pair Rydberg

The lowest A, excited states of C3H2are of Rydberg type, arising from the promotion of one electron from the carbene lone pair orbital to 3s and 3p Rydberg orbitals, are better represented by orbitals generated by a MCSCF/SD treatment (Table 9). 

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... 

The detection probability for a given trajectory depends on the fragment orientation (its Mj value) and the nature of the probe transition. All of these images were obtained via the two-photon Ilg XAS) transition. Five rotational branches are thus possible O, P, Q, R and S. The amplitudes for each of these two-photon transitions can be obtained from a sum of paired, Mj-dependent, one-photon amplitudes.37 The O branch, for example, consists of a contribution from a parallel P-type transition to a 7A virtual state, followed by a perpendicular P-type transition to the final 1ffs Rydberg (which is assumed to be ionized promptly). The product of those two transition amplitudes must be summed with another product in which the first transition is perpendicular and the second is parallel. The P and R branches consist of four contributions each and the Q branch has six such terms in its transition amplitude. The required one-photon amplitudes are taken from Ref. 37. 

Since the formation of high Rydberg states is not a major mechanism in Hj recombination, the presence of electric fields has litde or no effect on the total cross section. This is also the case with the ion-pair reaction since this proceeds via a... 

NBOs 3-5 are the three fluorine lone pairs ( LP ). As shown by the occupancies and hybrid composition, these lone pairs are inequivalent. LP(1) is the s-rich sigma-type sp0 26 lone pair (nF(cr) 79% s character), directed along the bond axis. LP(2) andLP(3) are the p-rich pi-type lone pairs (nF(7t) and nF(rf) 99.97% p-character), perpendicular to the bond axis. The lone pairs have occupancies slightly less than 2.000 00 (due to weak delocalization into Rydberg orbitals of the adjacent H), but overall, the correspondence with the elementary Lewis-structure description is excellent. 

Other experimental evidence leads to essentially the same conclusion regarding the n ionization of pyridine. El Sayed and Kasha (1961) have detected Rydberg series in the absorption spectrum similar to those in benzene and ascribable to n orbitals (9-266 e.v., 02 11-56 e.v., 62) and, in addition, reported a fragmentary series leading to a third ionization potential of 10-3 e.v. which they ascribed to the nitrogen lone pair. Similar values are found by photoelectron spectroscopy which also indicated the 10-3 e.v. (10-54 e.v.) level to be only weakly bonding. 

H. J. Neusser In reply to Prof. Woste let me mention that a situation similar to the high Rydberg states I discussed has been proposed for a dipolar bound electron in molecular anions. Here large distances of the electron and small binding energies are expected. First experimental indications were found. Ion pair states represent another interesting example. 

The He2A 2 state has nearly the same dissociation energy as the He (22J ion. This supports the idea that the excited He2 configurations can be described at small interatomic distances as an inner He core with an outer Rydberg orbital. This description is less quantitative for the heavier rare-gas pairs. The unusual maxima result either from curve crossing (e.g., C S ) or as for the state by a changeover in the... 

The experiments to measure final state distributions are done using the apparatus of Fig. 13.8. The stripper and 127° analyzer allow the analysis of the final Rydberg states. When an Ar+ ion beam is used the parent Ar+ beam is deflected from the neutral Ar n( charge exchange products by a pair of deflecting plates, and only the neutrals enter the concentric cylindrical stripper shown in Fig. 13.8. The outer cylinder is grounded, and the inner concentric cylinder is held at... 

Fig. 3. Schematic representation of the series (from the left to right) alkali-metal atom, cryptatium (expanded atom or radical contact-ion pair [Na+ c tris-bipy cryptandje ), electride (Rydberg atom or electron salt) [K+ c 9]e ).

If the collision system can separate asymptotically into a pair of charged particles of opposite signs, the attractive Coulomb tail of the interaction between them supports an infinite number of bound Rydberg states in each closed channel (with a threshold energy Eth). Its coupling with open channels, if any, normally turns these bound states into an infinite series of quasi-bound... 

The ES-mechanism of Frenkel-pair formation as a result of excitation of Rydberg atomic states was confirmed by recent molecular dynamics calculations [28,29]. After the bubble formation the surrounding ground state atoms appear to have moved to the second shell. It was found that the second-nearest neighboring vacancy-interstitial pairs could create the permanent defects, which remain in the lattice after exciton annihilation (Fig.Sb) [29],... 

Atomic cryocrystals which are widely used as inert matrices in the matrix isolated spectroscopy become non-inert after excitation of an electronic subsystem. Local elastic and inelastic lattice deformation around trapped electronic excitations, population of antibonding electronic states during relaxation of the molecular-like centers, and excitation of the Rydberg states of guest species are the moving force of Frenkel-pairs formation in the bulk and desorption of atoms and molecules from the surface of the condensed rare gases. Even a tiny probability of exciton or electron-hole pair creation in the multiphoton processes under, e.g., laser irradiation has to be taken into account as it may considerably alter the energy relaxation pathways. 

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