Rydberg functions

A different scheme must be used for determining polarization functions and very diffuse functions (Rydberg functions). It is reasonable to use functions from another basis set for the same element. Another option is to use functions that will depict the electron density distribution at the desired distance from the nucleus as described above. 

The MCSCF and the subsequent perturbation calculations were done using a 6-31+G basis set expanded by a set of spd Rydberg functions. Exponents of this additional gaussians were 0.032 and 0.028 for the s and p shells for the oxygen atom, and 0.023 and 0.021 for the carbon atom. For the d functions, a common value of 0.015 was chosen for both heavy atoms. 

Based on the same two step proeedure as presented above for C2H4 (MCSCF ealeulations followed by Schmidt orthogonalization of Rydberg functions), a systematic search was conducted by progressively incorporating groups of orbitals in the active space. Two types of wave functions proved well adapted to the problem, one for in-plane excitations, the other for out-of-plane excitations from the carbene orbital. The case of the Ai states will serve as an illustration of the general approach done for all symmetries and wave functions. 

Murrell and Sorbie have proposed an extended Rydberg function as... 

Coombs and Pethica, 1985 Chen and Hamers, 1991a). The error caused by force and deformation is much larger than the difference between the Morse function and the Rydberg function. 

The SAC-CI method can be applicable to various kinds of molecular spectroscopy excitation, ionization and electron-attached states in high accuracy. First, we overview the excitation [51 -53] and ionization spectra [51,54] of five-membered ring compounds, furan and thiophene. For these spectra, pioneering theoretical spectroscopy was performed by the SAC-Cl method [51] and has been followed by many theoretical works [52,53,55-58]. Comparisons of our old and new calculations show the importance of using the sufficiently flexible basis sets with valence and Rydberg functions as well as the reliable theory for the accurate descriptions of these spectra. We also explain the spectroscopy of p-benzoquinone (p-BQ), its anion radical [59], and aniline [60]. 

The general-/ method was also applied to the ground and excited states of polyatomic molecules acetylene and CNC. Some of the excited states of these molecules are described by the two-electron process. The DZP basis sets were used for acetylene and the DZP basis sets augmented with s- and p-type Rydberg functions = 0.023, Cp = 0.021 for C and = 0.028, [p = 0.025 for N) were used for CNC these Rydberg functions are important for of CNC. The general-/ method including / -operators up to... 

Ab Initio Calculations. All calculations on the electronic structures of CH3S are performed using the GAMESS program [122]. The calculations are based on the MCSCF and the FOCI methods. The standard 6-31G(d, p) basis set is used. To properly describe the excited states of CH3S, we have extended the basis set to include the Rydberg functions with = 0.023, = 0.020 and = 0.015 for the sulfur atom and = 0. = 0.040 for... 

MCSCF and the FOCI methods. The standard 6-31G(d,p) basis set [111] is used for all other calculations. To properly describe the excited states of thiophene, we have extended the basis set to include the Rydberg functions... 

The experimental ground-state geometry [138] was used with the molecule in the xy plane. ANO basis functions contracted as C,N/ Asl>pld, H/2sl/ , were used, supplemented with Islpld Rydberg functions in the cation charge centroid. The study of the electronic spectrum of imidazole involved tt— t7, 7t, and Rydberg states (in the gas... 

An analytical expression for the potential function ( extended-Rydberg function [11]) was based upon available data for re, We, cOeX . and De [12]. 

The vertical electronic spectrum of silanethione (H2Si=S 1) was investigated by using a multi-reference Cl method and an expanded AO basis set including 4s and 4p Rydberg functions. The equilibrium geometry of the X Ai ground state was determined... 

The AO basis is of VTZP quality plus diffuse s and p Rydberg functions. 

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