Bond Rydberg

In summary, an atom or molecule has many orbitals (core, bonding, non-bonding, Rydberg, and antibonding) available to it occupancy of these orbitals in a particular manner gives rise to a configuration. If some orbitals are partially occupied in this configuration. 

In a linear configuration thsA Bi state correlates with one component of n the other component, A, has been assigned to the second broad continuum centred around 128 nm, upon which is superimposed much more pronounced vibrational stmcture (see Fig. 3.1.4). Its appearance is similar to the X Ai Af photoelectron band (see Fig. 3.1.3) suggesting excitation of an electron from the H-H bonding orbital, 3ai, into the non-bonding Rydberg orbital,. This view... 

The bending frequency in the state of the molecular ion is almost identical to that in the neutral molecule However, the diffuseness and breadth of the band in the optical spectrum contrasts with the very sharp transition in the photoelectron band (see Fig. 3.1.3), and it is evident that the terminating orbital cannot be purely non-bonding, Rydberg. 

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 ... 

It is essential to keep in mind that all atoms possess excited orbitals that may become involved in bond formation if one or more electrons occupies these orbitals. Whenever aos with principal quantum number one or more unit higher than that of the conventional aos becomes involved in bond formation, Rydberg mos are formed. 

Rydberg Overlap is Strong and Bond Formation Occurs... 

The isomer lowest in energy is predicted to be the 2,5-dihydro-1,2,4-triazine 198g. The most stable structures always show two C=N double bonds. Moreover, in polar solvents, 198h should also be a dominant species [00PCCP2187]. The valence and Rydberg excited states of 1,2,3-triazine have been studied by multireference methods (MRD-CI) and the results are compared with experimental spectra [98CP39]. 

Electronic states and photodissociation dynamics of chloromethyl radical have been studied recently.114-117 Because of the chlorine substitution, there are several low-lying valence excited states (such as l2Ai and 22Bi, which mainly involve the orbitals on the CC1 bond) in addition to the 3s Rydberg state (22Ai), and more dissociation channels are available. 

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. 

We can divide the NAOs into the natural minimal basis (NMB), consisting of only the formal core and valence NAOs of simple bonding theory, and the natural Rydberg basis (NRB), consisting of everything else. With this partitioning, Eq. (3.24a) is expressed as... 

It is noteworthy that Rydberg orbital occupancies on the central atom (rY, final column of Table 3.29) are relatively negligible (0.01-0.03e), showing that d-orbital participation or other expansion of the valence shell is a relatively insignificant feature of hyperbonded species. However, the case of HLiH- is somewhat paradoxical in this respect. The cationic central Li is found to use conventional sp linear hybrids to form the hydride bonds, and thus seems to represent a genuine case of expansion of the valence shell (i.e., to the 2p subshell) to form two bonding hybrids. However, the two hydride bonds are both so strongly polarized toward H (93%) as to have practically no contribution from Li orbitals, so the actual occupancy of extra-valent 2pu orbitals ( 0.03< ) remains quite small in this case. 

Below the photoionisation threshold a core electron in a free molecule can be excited into empty anti-bonding molecular orbitals (m.o. s) as well as into Rydberg states. These transitions are observable as sharp features directly below the corresponding absorption edge (carbon K, oxygen K etc.). Above the... 

Rydberg series were detected in molecular spectra in the early 1930 s, notably by W. C. Price who showed that they arose from the outer electrons. These can usually be fairly well classified in terms of the structure of the molecule, e.g. non-bonding electrons on particular atoms or electrons of double bond systems. Non-bonding electrons give more nearly atomic Rydberg series, with many numbers observable, and correspondingly accurate ionization potentials have been recorded. Most of the earlier measurements belong to this class. 

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. 

An electronic transition in which an electron is promoted from a bonding a orbital to an antibonding a orbital. The transition energies are often close to those of Rydberg transitions. See Absorption Spectroscopy Comm, on Photochem. (1988) Pure and Appl. Chem. 60, 1055. 

If the electron enters a Rydberg orbital on one of the protonated amine sites, in addition to undergoing a cascade of radiative or non-radiative relaxation steps to lower-energy Rydberg states, it can subsequently undergo intra-peptide electron transfer to either an SS cr or an OCN n orbital after which disulfide or N-Cr, bond cleavage can occur [3r,3u-3w]. 

Figure 3 Energies, as functions of the S-S bond length, of the parent charged polypeptide (top), of ground and excited-Rydberg states localized on the protonated amine side chain, and of the SS CT -attached state in the absence of (upper curve) and in the presence of (lower curve) Coulomb stabilization (appears as Figure 1 in ref. 3s).

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