Spectroscopy LCAO

OH species, 30 249 olefin, 25 138, 139 on oxide semiconductors, 7 47 of oxygen, 27 192 relative contents of various forms of in absence of illumination, 23 161-164 on illumination, 23 164-170 SCF-LCAO-MO procedure, 25 35, 36 of simple molecules, 34 166-174 sites for, 26 360, 361 uniformity of, 26 361, 362 spectroscopy, 25 198-202 of spillover hydrogen, the kinetics of, 34 7 surface diffusion as rate-determining step, 34 7... 

Vibrational 57) and F NMR 68) spectroscopy were used to establish for CIF3O2 the following structure of symmetry C v, which according to semi-empirical linear combination of atomic orbitals-molecular orbitals (LCAO-MO) self-consistent field (SCF) calculations 239) is most stable ... 

Bell, C.F., R.D. Beauchamp, and E.L. Short, Borate complexation withpentitols a study by nB-N.M.R. spectroscopy andMNDO semi-emperical LCAO-MO calculations. Carbohydrate Research, 1989.185 p. 39-50. 

The 1,3,4-thiadiazole ring system, with three heteroatoms, does not exhibit tautomerism in its fully conjugated form. However, when certain substituents are present, tautomerism is possible. l,3,4-Thiadiazolin-2-ones (39 X = 0) and -2-thiones (39 X = S) exist in the oxo and thione forms, respectively, as shown by spectroscopic and LCAO-MO calculations. 2-Amino-l,3,4-thiadiazoles exist in the amino form in solution and in the solid state the Kt value is 10s as shown by basicity measurements. UV spectroscopy and LCAO-MO calculations show that the amino tautomer is also the main species when there is an alkoxy group in the 5-position (40 R1 = alkoxy, R2 = NH2), or if the exocyclic nitrogen atom is part of a hydrazone group (40 R2 = NHN=CR2). 

NMR spectroscopy used in conjunction with lanthanide shift reagents supports the application of LCAO-SCF calculations to 1,2,4-triazoles (74JOC357). 

Jhe perimeter model introduced by Platt (1949), reformulated in the LCAO Mo form by Moffitt (1954a), and extended by Gouterman (1%1), Heilbron-ner and Murrell (1%3), and Michl (1978), has been very useful in understanding trends in the electronic spectra of cyclic Jt systems. It applies equally to singlet and triplet states and has provided the commonly used nomenclature for both. The following discussion is limited to the singlet states, which are more important in ordinary spectroscopy. 

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