Electron configurations excited state

A CASSCF calculation is a combination of an SCF computation with a full Configuration Interaction calculation involving a subset of the orbitals. The orbitals involved in the Cl are known as the active space. In this way, the CASSCF method optimizes the orbitals appropriately for the excited state. In contrast, the Cl-Singles method uses SCF orbitals for the excited state. Since Hartree-Fock orbitals are biased toward the ground state, a CASSCF description of the excited state electronic configuration is often an improvement. 

The solution to this apparent paradox lies in the photoionization dynamics. Clearly, the form of the parent ion signal depends strongly on the specific photoionization dynamics and, in order to avoid misleading conclusions, must be analyzed for each specific case. The (Koopmans) photoionization correlations of excited-state electronic configurations with those of the cation play a critical role. 

Figure 5.37. Ground- and excited-state electronic configurations of [Fe(C5Me5)2] and TCNE species. Adapted from Miller, J. S. Calabrese, J. C. Rommelmann, H. Chittipeddi, S. R. Zhang, J. H. Reiff, W. M. Epstein, A. J. J. Am. Chem. Soc., 1987,109, 769. Copyright 1987 American Chemical Society.

Ground-State and excited-state electronic configurations of confugated dienes and trienes. 

Ground-state and excited-state electronic configuration of conjugated dienes and trienes. ... 

Figure 7.3 Ground state and singlet and triplet excited state electron configurations.

For the two-helium excited state electron configurations, we can write three product two-electron symmetric spin functions,... 

In the presence of light, lowest unoccupied molecular orbital (LUMO) of the ground state becomes HOMO of the excited state known as photochemical HOMO. The excited state electronic configuration of allyl radical is Pi P3. ... 

TABLE 1 Ground-State (GS) and Selected Excited-State Electronic Configurations of Rare Earth Cations ... 

The excited electron in the a antibonding orbital is in a molecular orbital that has 2u symmetry, and the electron still in the tt orbital has Ilg symmetry. The direct product of these two symmetries is simply Hg. (Verify this.) The a and tt electrons can have either the same direction spin or different direction spin (rather, the z components of their spin), so multiplicities of 3 or 1 are possible. Therefore, the term symbols for this excited-state electron configuration are and II states are doubly degenerate. In this case, there are two possible, degenerate tt molecular orbitals for the unexcited electron. Complete term symbols would have values for ft included. For the triplet state, H can be 2,1, or 0. For the singlet state, Q, can only be 1. Unlike atomic term symbols, it is relatively uncommon to see the fi values listed explicitly in the term symbols of diatomic molecules. One would see Ilu to represent all three individual states, rather than Ilu 2> Ilu i, and Ilu o-... 

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