The photolysis of gaseous aldehydes. II. The decomposition of formyl and acetyl radicals

1956 ◽  
Vol 9 (1) ◽  
pp. 34 ◽  
Author(s):  
FH Dorman ◽  
AS Buchanan
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Kcal Mole ◽  
Correct Order ◽  
Order Of Magnitude ◽  
Energy Surfaces ◽  
Parameter Values

The potential energy surfaces for the decomposition of HCO, CH3CO, and COCl radicals have been constructed using Bawn's (1938, 1939) method with new parameter values. The values obtained for the energies of activation for decomposition were of the order of 26, 18, and 6 kcal mole-1 respectively. The CH3CO and COCl values agree with experimental estimates and consequently it is believed that the formyl value is of the correct order of magnitude.

Internal conversion and the crossing of molecular potential energy surfaces

1962 ◽  
Vol 268 (1335) ◽  
pp. 437-451 ◽  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Internal Conversion ◽  
Careful Analysis ◽  
Molecular Potential ◽  
Order Of Magnitude ◽  
Molecular Potential Energy ◽  
Energy Surfaces ◽  
New Formula ◽  
Crossing Point

A re-examination is made of the Landau-Zener formula relating to the probability of an electronic jump near the crossing-point of two potential energy curves (or surfaces). Three cases are distinguished: discrete-discrete, discrete-continuum and continuum-continuum transitions. Different formulae are obtained for each of these cases. These formulae involve certain matrix elements of the interaction between the energy curves. A careful analysis is made of the order of magnitude of the terms that appear, and some corrections are made of previous work. It appears that the limits within which the original Landau-Zener formula is valid are seldom found in actual practice. A new formula (50) of greater validity is presented.

scholarly journals Diagonal Born-Oppenheimer Corrections to the Ground Electronic State Potential Energy Surfaces of Ozone: Improvement of Ab Initio Vibrational Band Centers for the 16O3, 17O3 and 18O3 Isotopologues

2020 ◽  
Author(s):  
Attila Tajti ◽  
Péter Szalay ◽  
Roman V. Kochanov ◽  
Vladimir G. Tyuterev
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Vibrational States ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
State Potential ◽  
Effective Models ◽  
Energy Surfaces ◽  
Mass Dependent

<div>Mass-dependent diagonal Born-Oppenheimer corrections (DBOC) to the ab initio electronic ground state potential energy surface for tseveral isotopologues of the ozone molecule are reported for the first time. The comparison with experimental band centers shows a significant improvement of the accuracy with respect to the best Born-Oppenheimer (BO) ab initio calculations reducing the total root-mean-squares (calculated - observed) deviations by about factor of two. For the set of 16O3 vibrations up to five bending and four stretching quanta, the mean (calculated - observed) deviations drop down from 0.7 cm-1 (BO) to about 0.1 cm-1, with the most pronounced improvement seen for bending states and for mixed bend-stretch polyads. In case of bending band centers directly observed under high spectral resolutions, the errors are reduced by more than order of magnitude from observed levels, approaching nearly experimental accuracy. New sets of ab initio vibrational states can be used for improving spectroscopic effective models for analyses of observed high-resolution spectra, particularly in cases of accidental resonances with ,,dark'' states requiring accurate theoretical predictions.</div>

The spectrum of singlet SiH2

2004 ◽  
Vol 82 (6) ◽  
pp. 694-708 ◽  
Author(s):  
S N Yurchenko ◽  
P R Bunker ◽  
W P Kraemer ◽  
P Jensen
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Emission Spectra ◽  
Theoretical Work ◽  
Fluorescence Studies ◽  
Analytical Functions ◽  
Dispersed Fluorescence ◽  
Energy Surfaces ◽  
Parameter Values

We report a theoretical study of the two lowest singlet electronic states ([Formula: see text]1A1 and Ã1B1) of silylene SiH2. These states become degenerate as a 1Δg state at linear configurations and are subject to the Renner effect. In ab initio calculations we have determined the potential energy and dipole moment surfaces for each state, and the transition moment surface between the states. Parameterized analytical functions have been fitted through the various sets of ab initio points, and the parameter values obtained for the potential energy surfaces have been further refined in fittings to experimental spectroscopic data. In these latter fittings, we use as input data experimentally derived energy differences together with ab initio points. In this manner, we achieve refined potential energy surfaces that behave reasonably also in regions of configuration space that are not sampled by the wavefunctions of the states for which experimentally derived energies are available. The calculation of rovibronic energies, the fittings to experimentally derived energies, and simulations of Ã1B1 → [Formula: see text]1A1 emission spectra of SiH2 have been carried out with the RENNER program system. The higher excited vibrational states of [Formula: see text]1A1 SiH2 form polyads of heavily interacting states and many polyad states have been observed in dispersed fluorescence studies. The present theoretical work shows that owing to the heavy interaction between the states in the polyads, it is difficult to obtain unambiguous assignments for them.Key words: silylene, RENNER, ab initio.PACS Nos.: 31.15.Ar, 33.20.Wr, 33.20.Ea

scholarly journals Diagonal Born-Oppenheimer Corrections to the Ground Electronic State Potential Energy Surfaces of Ozone: Improvement of Ab Initio Vibrational Band Centers for the 16O3, 17O3 and 18O3 Isotopologues

2020 ◽  
Author(s):  
Attila Tajti ◽  
Péter Szalay ◽  
Roman V. Kochanov ◽  
Vladimir G. Tyuterev
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Vibrational States ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
State Potential ◽  
Effective Models ◽  
Energy Surfaces ◽  
Mass Dependent

<div>Mass-dependent diagonal Born-Oppenheimer corrections (DBOC) to the ab initio electronic ground state potential energy surface for tseveral isotopologues of the ozone molecule are reported for the first time. The comparison with experimental band centers shows a significant improvement of the accuracy with respect to the best Born-Oppenheimer (BO) ab initio calculations reducing the total root-mean-squares (calculated - observed) deviations by about factor of two. For the set of 16O3 vibrations up to five bending and four stretching quanta, the mean (calculated - observed) deviations drop down from 0.7 cm-1 (BO) to about 0.1 cm-1, with the most pronounced improvement seen for bending states and for mixed bend-stretch polyads. In case of bending band centers directly observed under high spectral resolutions, the errors are reduced by more than order of magnitude from observed levels, approaching nearly experimental accuracy. New sets of ab initio vibrational states can be used for improving spectroscopic effective models for analyses of observed high-resolution spectra, particularly in cases of accidental resonances with ,,dark'' states requiring accurate theoretical predictions.</div>

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

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