Molecular Rydberg states calculation method

It should be noted, however, that in actual situations the final states of the shakeup process are molecular Rydberg states and should be described by the MO wave functions. We estimated the contributions from the shakeup probabilities for atoms accompanying A -shell PI to the total (shakeup-plus-shakeoff) probabilities. The shakeup probabilities were calculated with the HS wave functions as the overlap integrals by the method used in our previous work [47]. The shakeup probabilities in PI were found to be about 30 40% of the total probabilities for 3p electrons and about 40 50% for 3d electrons. These large shakeup probabilities suggest that the chemical effect on the shakeup process would be large if the shakeup probabilities are calculated with the MO wave functions and the contributions of the shake process in PI to the Kf3/Ka ratios for 3d elements would be appreciable. 

Ab initio calculations were carried out for all the low-lying non-Rydberg states of the systems N2, 02, NO, Of, and NO+. In N2, for example, there are 102 molecular states that result from nitrogen atoms in the lowest 4S, 2D, and 2P states. These states were all uniformly described using VCI wave functions constructed as described in Section II. Minimum basis, double-f basis and double-f-plus-polarization basis sets were employed for these studies. For the minimum basis-set calculations, which were always carried out first, the VCI wave functions represent full Cl projections with the constraint that the K shells were kept frozen for all states. However, no constraint on the 2og and 2ou orbitals was made since a Cl among these orbitals is necessary to ensure proper description of the hole states in these molecules, such as C3n of N2. The calculations all have the property of asymptotically connecting with the correct atomic states. This computational method has previously been applied, with reliable results, to both closed- and open-shell systems.6 9 11... 

These methods lead in general to very good agreement between calculated and observed quantities. Rydberg states are also described well. They are characterized by high quantum number orbitals, which are much more extended than valence orbitals. Molecular Rydberg orbitals resemble atomic orbitals since an electron in such an orbital is so far from the nuclei of the... 

Several attempts have been made to include Rydberg states within the INDO/S scheme, but they have not proven generally useful. See for example, D. R. Salahub and C. Sandorfy, Theor. Chim. Acta, 20, 111 (1971). CNDO, INDO, and RCNDO-CI Calculations on the Electronic Spectra of Saturated Hydrocarbons. W. Haque, /. Chon. Phys., 67, 3629 (1977). Use of the RINDO Method in Spectroscopy. Molecular Rydberg S -S and T<-T Transitions. 

From among Sandorfy s subsequent theoretical projects, two in particular should be mentioned the first treatment of the excited states and electronic spectra of saturated hydrocarbons9 by a new rc-electron method of the Pariser-Parr type, and the first attempt to introduce Rydberg orbitals into molecular orbital calculations.10... 

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]. 

Rydberg-Klein-Dunham potential curves have been constructed for the states X rir and A 2A using the molecular constants of [7] and [37] (publication in [8]) these have been combined with theoretical (ab initio MCSCF-CI) curves for the X and A states to obtain also the short- and long-range parts of the curves MCSCF-CI potential curves have also been calculated for the unobserved excited states (repulsive) and (quasidissociative) [14]. Potential curves have been calculated for the states X rir, a 2", (quasidissociative), and (repulsive) with the dissociation limit P+(3P) + H(2S) and for the states A A, 2S+ (quasidissociative), and (repulsive) with the dissociation limit P+( D) + H(2S) using the MRD Cl method the results are shown in Fig. 2 along with further possible dissociation limits and corresponding excited states of PH+ [18, 19]. 

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