Rydberg excited state

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]. 

The MS-CASPT2 method should be used when it is suspected that several CASSCF states are close in energy, a situation that often obtains in photochemistry where close avoided crossings are common and even conical intersections. It may also be crucial in order to separate valence and Rydberg excited states as illustrated in the original publication for the case of ethylene. Another example was given by Merchan and Serrano-Andres in a study of the excited states of n-tetrasilane [52],... 

Rydberg excited states of ANI and its derivatives have been located72,143. A novel band located between the first and second it — n transitions, and centered at 37104 cm-1 (4.62 eV above the Sq and 0.38 eV above the, Y state), has been observed72. This singlet 1 B state has been assigned to a 3s-Rydberg state161. 

The electronic absorption spectrum of CH3CN has been recorded and discussed extensively Many transitions to Rydberg excited states have been observed... 

The formation of a negative ion state by Feschbach resonance (temporary binding of an electron to PH3 in a Rydberg excited state) was discussed [3]. 

Even though molecular mechanics and semiempirical methods are capable of describing a great many molecular properties, and more are being added every year, certain properties are beyond the scope of either approach. In such cases ab initio methods may offer the only theoretical model capable of attacking the problem. For example, neither method can accurately treat the manifold of valence and Rydberg excited states of linear polyenes. Nor can they handle the hyperfine spin properties of first- or second-row elements. 

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