Abinitio calculation of the vibrational structure in the electronic spectra of HCN and DCN between 1700 and 2000 Å

1977 ◽  
Vol 55 (20) ◽  
pp. 3664-3675 ◽  
Author(s):  
M. Perić ◽  
S. D. Peyerimhoff ◽  
R. J. Buenker
Keyword(s):  
Excited States ◽  
Band System ◽  
Vibrational Structure ◽  
Electronic Transitions ◽  
Dissociation Limit ◽  
Potential Surfaces ◽  
Double Zeta ◽  
Polarization Functions ◽  
Franck Condon ◽  
Ci Calculations

Ab initio SCF and CI calculations for the potential surfaces of HCN in ground and various 1(π,π*) excited states are carried out using an AO basis of double-zeta quality augmented with various polarization functions. These results are then combined with transition moment data to allow for a Franck-Condon analysis of the vibrational structure of the lowest three electronic transitions in both HCN and DCN. The resulting intensity distribution is then compared with the corresponding experimental data reported by Herzberg and Innes. This work confirms the earlier conclusion of Schwenzer et al. that the upper state in the [Formula: see text] band system is the 1∑−−1A″species, and not the 1Δ as originally believed. In addition a detailed mechanism for the observed predissociation of the α state is outlined, in which the gradual conversion of the π* MO of bent HCN into a pure hydrogenic 1s AO plays a key role. Arguments are also presented in favor of assigning the [Formula: see text]transition seen in DCN to a 1Δ-21A′ upper state with the same D + CN dissociation limit as for the 1∑−−1A″ species.

Angeregte Zustände des Fluormoleküls

1974 ◽  
Vol 29 (10) ◽  
pp. 1425-1430 ◽  
Author(s):  
E. Kasseckert ◽  
B. Wirsam
Keyword(s):  
Excited States ◽  
Band System ◽  
Stable States ◽  
Ci Calculations ◽  
Potential Curves

Abstract For the lower lying excited states of the fluorine molecule elaborated SCF-CI calculations have been carried out. The discussion of the potential curves of some higher excited stable states leads to the conclusion that the experimentally observed orange band-system may belong to two transitions 1Σg+ - 1Πu and 1Σu- - 1Πg .

scholarly journals Franck-Condon factors and observed band strength distribution in the vibrational structure of the Ag2 D-X band system

2010 ◽  
Vol 75 (5) ◽  
pp. 659-667 ◽  
Author(s):  
Ankica Antic-Jovanovic ◽  
Milos Momcilovic ◽  
Vojislav Bojovic ◽  
Murtadha Khakoo ◽  
Russ Laher
Keyword(s):  
Band System ◽  
Strength Distribution ◽  
Vibrational Structure ◽  
Isotopic Effect ◽  
Molecular Constants ◽  
Band Origin ◽  
Isotopic Shifts ◽  
X Band ◽  
Condon Factors ◽  
Franck Condon

Potential curves for the X1?g+ and D1?u+ states of three diatomic silver isotopomers, 107Ag2, 107Ag109Ag and 109Ag2, were determined from the best available molecular constants by the Rydberg-Klein-Rees method. From these potentials, Franck-Condon factors and band-origin wave numbers were computed, and the reliability of the obtained values was verified by comparison with the observed band strength distribution and the measured band origin positions in a previously recorded D-X spectrum. The ratios of the Franck-Condon factors to those of corresponding isotopic bands were found to be very close to unity, revealing only a very small isotopic effect on the Franck Condon factors of Ag2 D-X bands. The isotopic shifts of the calculated band origins agree well with previously measured displacements of band heads.

Electronic States of Aromatic Hydrocarbons: The Franck-Condon Principle and Geometries in Excited States

1962 ◽  
Vol 15 (4) ◽  
pp. 573 ◽  
Author(s):  
EF McCoy ◽  
IG Ross
Keyword(s):  
Excited States ◽  
Aromatic Hydrocarbons ◽  
Strain Energy ◽  
Electronic Transitions ◽  
Bond Orders ◽  
Polycyclic Aromatics ◽  
Aromatic Rings ◽  
Bond Strain ◽  
Length Changes ◽  
Franck Condon

It is suggested that electronic transitions in aromatic hydrocarbons can profitably be characterized by a quantity R, where R2 is the sum of the squares of the bond length changes accompanying the transition. R determines, via the Franck-Condon principle, the distribution of intensity within the vibrational envelope of a transition. In polycyclic aromatics, values of R can be extracted from solution spectra, if the intervals of about 1400 cm-1 which commonly separate the vibrational peaks are interpreted as defining quasi-progressions in a skeletal bond displacement vibration. Values of R so determined are compared with values computed from bond orders in excited states, using the wave-functions of Pariser. Such comparisons are made for benzene, naphthalene, azulene, and anthracene. Agreement is good. The calculated bond orders are tabulated. In an Appendix, bond angles in aromatic rings are calculated on the assumption that the observed angles minimize the σ-bond strain energy. Angles are calculated for the ground states of naphthalene and anthracene, and for two excited states of naphthalene. The excited state geometries so deduced are depicted.

Theoretical study of the vibrational structure of the 1(n,π*) transition in diimide: potential curves and Franck–Condon analysis

1977 ◽  
Vol 55 (9) ◽  
pp. 1533-1545 ◽  
Author(s):  
M. Perić ◽  
R. J. Buenker ◽  
S. D. Peyerimhoff
Keyword(s):  
Band Structure ◽  
Excited States ◽  
Electronic Transition ◽  
Isotope Shift ◽  
Theoretical Study ◽  
Vibrational Structure ◽  
Absorption System ◽  
Electronic Transition Moment ◽  
Franck Condon ◽  
Potential Curves

Ab initio CI potential curves are reported for the ground and 1(n,π*) excited states of diimide for each of the six possible internal coordinates. These results are then used to obtain vibrational wavefunctions and frequencies for both states, which in turn are combined with electronic transition moment data to allow a Franck–Condon analysis of the band structure of the (dipole-forbidden) n–π* absorption system. This procedure allows one to reproduce the main features of the observed spectra of N2H2 and N2D2 and indicates that the majority of the vibrational transitions seen are vibronically induced via the antisymmetric NH stretching mode v5. The calculations are in essential agreement with the earlier experimental interpretation of the vibrational structure of this transition in terms of progressions in the symmetric bending (v2) and NN stretching (v3) frequencies, except that they indicate that the previous v2′ numbering should be altered by three units. According to this interpretation the isotope shift for the vibronic origin is 672 cm−1 compared with the corresponding calculated value of 666 cm−1. It is argued that several other weaker transitions seen experimentally arise via a different inducement mechanism, namely the torsion (v4) mode, and as such are only observed in energy regions where v5-induced transitions cannot occur.

The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)

2003 ◽  
Vol 68 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Stanislav Záliš ◽  
Antonín Vlček ◽  
Chantal Daniel
Keyword(s):  
Excited States ◽  
Substitution Effect ◽  
Electronic Transitions ◽  
Ligand Field ◽  
Metal Carbonyls ◽  
Electron Density Redistribution ◽  
Time Resolved ◽  
Model Complex ◽  
Td Dft ◽  
Time Resolved Infrared Spectroscopy

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.

An SCF and MRD-CI study of the ground and excited states of the He + H2 system. I. Calculated potential surfaces

1978 ◽  
Vol 34 (3) ◽  
pp. 403-422 ◽  
Author(s):  
Joachim Römelt ◽  
Sigrid D. Peyerimhoff ◽  
Robert J. Buenker
Keyword(s):  
Excited States ◽  
Potential Surfaces
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