The structure and vertical excitation energies of the chlorothioformyl radical, ClCS: implications for the photofragmentation of thiophosgene

1993 ◽  
Vol 71 (1) ◽  
pp. 112-117 ◽  
Author(s):  
M. Hachey ◽  
F. Grein ◽  
R. P. Steer
Keyword(s):  
Energy Level ◽  
Ab Initio ◽  
Excited States ◽  
Ground State ◽  
Excited Electronic State ◽  
Excitation Energies ◽  
Electronically Excited States ◽  
Vertical Excitation ◽  
Electronically Excited ◽  
Vertical Excitation Energies

Ab initio CI studies have been performed to determine the geometry of the ground and first electronically excited states of the chlorothioformyl radical, ClCS, and the vertical excitation energies of its ten lowest doublet states and two lowest quartet states. The results are used to construct a more complete energy level correlation diagram for the photofragmentation of Cl2CS. The lowest excited electronic state of ClCS lies only 0.79 eV (adiabatic) above the ground state. Its discovery indicates that the results of previous photofragmentation experiments may need to be reinterpreted.

The ground state and low-lying excited states of CCCN radical and its ions: a CASSCF/CASPT2 study

2016 ◽  
Vol 94 (9) ◽  
pp. 803-807
Author(s):  
Angyang Yu
Keyword(s):  
Excited States ◽  
Ground State ◽  
Linear Structure ◽  
Electronic Configuration ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Excitation Energies ◽  
Complete Active Space ◽  
Vertical Excitation

The ground state and low-lying excited states of the CCCN radical and its ions have been investigated systematically using the complete active space self-consistent field (CASSCF) and multi-configuration second-order perturbation theory (CASPT2) methods in conjunction with the ANO-RCC-TZP basis set. The calculated results show that the state 12Σ+ has the lowest CASPT2 energy among the electronic states. By means of the geometric optimization of this radical, it could be found that the molecule exhibits linear structure, with the bond lengths R1 = 1.214 Å, R2 = 1.363 Å, R3 = 1.162 Å, which are very close to the experimental values. The calculated vertical excitation energies and the corresponding oscillator strengths show that there are three relatively strong peaks at energies 0.63, 4.04, and 5.49 eV, which correspond to the transitions 12Σ+ → 12Π, 12Σ+ → 22Π, and 12Σ+ → 22Σ+, respectively. Additionally, the electronic configuration and the harmonic vibration frequencies of each state are also investigated.

scholarly journals AN AB INITIO STUDY OF ELECTRONICALLY EXCITED STATES OF SiN AND SO

2021 ◽  
Author(s):  
Gap-Sue Kim ◽  
Sergei Yurchenko ◽  
Mikhail Semenov ◽  
Wilfrid Somogyi ◽  
Nicholas Clark ◽  
...  
Keyword(s):  
Ab Initio ◽  
Excited States ◽  
Electronically Excited States ◽  
Electronically Excited

MR-CISD and MR-AQCC Calculation of Excited States of Malonaldehyde: Geometry Optimizations Using Analytical Energy Gradient Methods and a Systematic Investigation of Reference Configuration Sets

2003 ◽  
Vol 68 (3) ◽  
pp. 447-462 ◽  
Author(s):  
Silmar A. do Monte ◽  
Michal Dallos ◽  
Thomas Müller ◽  
Hans Lischka
Keyword(s):  
Excited States ◽  
Ground State ◽  
Transition Energy ◽  
Gradient Methods ◽  
Systematic Investigation ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Band Maximum ◽  
Vertical Excitation ◽  
Energy Gradient

Extended MR-CISD and MR-AQCC calculations have been performed on the ground state and the first two excited states of malonaldehyde. Full geometry optimizations have been carried for Cs and C2v structures both at MR-CISD and MR-AQCC levels. Vertical and minimum-to-minimum excitation energies and oscillator strengths have been computed. Systematic studies have been undertaken concerning several types of reference spaces. Agreement with the experimental 0-0 transition energy to the S1 state (expt. 3.50 eV, calc. 3.56 eV) and for the vertical excitation to S2 (expt. band maximum 4.71 eV, best estimate 4.86 eV) is very good. In agreement with the CASSCF/CASPT2 results by Sobolewski and Domcke (J. Phys. Chem. A 1999, 103, 4494), we find that the hydrogen bond in malonaldehyde is weakened by excitation to the S1 state. The barrier for proton transfer in the S1 state is increased in comparison with the ground state.

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