Energy level diagram molecular structure

The mathematical pictures called "electron density maps" are used to determine molecular structures and the energy level diagrams are used to determine the energies of bond formation and to interpret spectroscopy data. 

A schematic energy level diagram for conjugated polyenes is shown in Fig. 3.5.1. It is obvious that the chemical and physical properties of these compounds are mostly controlled by the orbitals within the dotted lines i.e., the jt and 7r molecular orbitals, as well as the nonbonding orbitals, if there are any. Hence, to study the electronic structure of these systems, as a first approximation, we can ignore the a and a orbitals and concentrate on the jt and jt orbitals. 

Molecular Systems. Molecules present a considerably more complex picture. Illustrated in Figure 3 is the energy level diagram for OH, the hydroxyl radical. The structure consists of several electronic states, each of which supports a number of vibrational states. Rotational motion is superimposed on each electronic-vibrational state as illustrated in Figure 3b. OH is an attractive molecule for analysis because of its dominant importance in combustion kinetic schemes and because its structure, while more complicated than any atom s, is fairly simple compared to many other molecules. 

Figure 145 (a) The cross-section of an edge emitting DL LED supposed to act as an electrically pumped organic laser (b) the molecular structure of Nile Blue (NB) and (c) the energy level diagram for the device. Adapted from Ref. 555. 

Sphalerite (p-ZnS) has a cubic crystal structure in which both Zn and S occur in regular tetrahedral coordination. Pure sphalerite is a diamagnetic semiconductor with a large band gap (—3.6 eV Shuey, 1975). On the basis of the observed structure and properties, the simple MO energy-level diagram shown in Fig. 6.1 can be proposed to describe the bonding in a ZnS4 cluster molecular unit. Overlaps between outermost s and p... 

Fig. 6.10. Electronic structure of pyrite (a) molecular-orbital energy-level diagram (modified after Burns and Vaughan, 1970) (b) schematic one-electron energy-band diagram. Numbers in brackets refer to the number of electron states per molecule available. is the Fermi level hatched bands are filled with electrons (modified after Either et al., 1968 Goodenough, 1972).

Fig. 6.17. Electronic structure models for FeS (a) molecular-orbital energy levels for the FeSj" octahedral cluster calculated using the MS-SCF-Za method, for low-spin Fe + (singlet, as in pyrite) and high-spin Fe + (quintet) states (after Tos-sell, 1977) (b) electron structure model for pyrrhotite based on calculated energy levels for the FeSe " cluster (from Tossell, 1977) and sulfur Ai(3 emission and K absorption spectra (Diagram after Sakkopoulos et ah, 1984) (c) schematic energy-level diagram for the troilite form of FeS (after Goodenough, 1967).

The ion H3 has been observed, but its structure has been the subject of some controversy. Prepare a molecular orbital energy level diagram for H3, assuming a cyclic structure. (The same problem for a linear structure is given in Exercise 5-4.)... 

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