ChemInform Abstract: Photoelectron Spectra of the Excited States of an Intermediate Case Molecule: Pyrazine.

ChemInform ◽  
1990 ◽  
Vol 21 (20) ◽  
Author(s):  
S. HILLENBRAND ◽  
L. ZHU ◽  
P. JOHNSON
Keyword(s):  
Excited States ◽  
Photoelectron Spectra ◽  
Intermediate Case

Photoelectron spectra of the excited states of an intermediate case molecule: Pyrazine

1990 ◽  
Vol 92 (2) ◽  
pp. 870-874 ◽  
Author(s):  
Susan Hillenbrand ◽  
Langchi Zhu ◽  
Philip Johnson
Keyword(s):  
Excited States ◽  
Photoelectron Spectra ◽  
Intermediate Case

Time-resolved photoelectron spectra of optically excited states in Pd3−

2001 ◽  
Vol 114-116 ◽  
pp. 163-167 ◽  
Author(s):  
N. Pontius ◽  
P.S. Bechthold ◽  
M. Neeb ◽  
W. Eberhardt
Keyword(s):  
Excited States ◽  
Photoelectron Spectra ◽  
Time Resolved

scholarly journals Highly-Excited State Properties of Cumulenone Chlorides in the Vacuum-Ultraviolet

2020 ◽  
Author(s):  
Quynh Nguyen ◽  
William Peters ◽  
Ryan Fortenberry
Keyword(s):  
Excited States ◽  
Vacuum Ultraviolet ◽  
Lone Pair ◽  
Carbon Chain ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Chain Elongation ◽  
Electronic Excitations ◽  
Quantum Chemical Analysis ◽  
Poten Tials

<div><div><div><p>Recent observations of chloromethane in interstellar environments suggest that other organohalo- gens, which are known to be critically important in Earth′s atmosphere, may also be of significance beyond our own terrestrial veil. This raises the question of how such molecules behave under extreme conditions such as when exposed to vacuum ultraviolet (VUV) radiation. VUV photons promote molecules to highly excited states that fragment in non-statistical patterns controlled by the initial femtosecond dynamics. A detailed understanding of VUV-driven photochemistry in complex organic molecules that consist of more than one functional group is a particularly challenging task. This quantum chemical analysis reports the electronic states and ionization potentials up to the VUV range (6 - 11 eV) of the chlorine-substituted cumulenone series molecules. The valence and Rydberg properties of lone-pair terminated, π-conjugated systems are explored for their potential resonance with lone pairs from elsewhere in the system. The carbon chain elongation within the family ClHCnO, where n=1-4, influences the electronic excitations, associated wavefunctions, and ionization poten- tials of the molecules. The predicted geometries and ionization potentials are in good agreement with the available experimental photoelectron spectra for formyl chloride and chloroketene, n=1-2. Furthermore, comparison between the regular cumulenone species and the corresponding chlorinated derivatives exhibit similar behaviors especially for n=3, where the allene backbone in propadienone chloride is severely bent. Most notably for the excited states is that the Rydberg character becomes more dominant as the energy increases, with some retaining valence characters.</p></div></div></div>

scholarly journals Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

2016 ◽  
Vol 113 (7) ◽  
pp. 1698-1705 ◽  
Author(s):  
Marissa L. Weichman ◽  
Jessalyn A. DeVine ◽  
Daniel S. Levine ◽  
Jongjin B. Kim ◽  
Daniel M. Neumark
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Cross Sections ◽  
Electronic Spectroscopy ◽  
Spectroscopic Characterization ◽  
Photoelectron Spectra ◽  
Velocity Map Imaging ◽  
Vibronic Structure ◽  
Quantum Chemistry Calculations ◽  
Franck Condon

Polycyclic aromatic hydrocarbons, in various charge and protonation states, are key compounds relevant to combustion chemistry and astrochemistry. Here, we probe the vibrational and electronic spectroscopy of gas-phase 9-, 1-, and 2-anthracenyl radicals (C14H9) by photodetachment of the corresponding cryogenically cooled anions via slow photoelectron velocity-map imaging (cryo-SEVI). The use of a newly designed velocity-map imaging lens in combination with ion cooling yields photoelectron spectra with <2 cm−1 resolution. Isomer selection of the anions is achieved using gas-phase synthesis techniques, resulting in observation and interpretation of detailed vibronic structure of the ground and lowest excited states for the three anthracenyl radical isomers. The ground-state bands yield electron affinities and vibrational frequencies for several Franck–Condon active modes of the 9-, 1-, and 2-anthracenyl radicals; term energies of the first excited states of these species are also measured. Spectra are interpreted through comparison with ab initio quantum chemistry calculations, Franck–Condon simulations, and calculations of threshold photodetachment cross sections and anisotropies. Experimental measures of the subtle differences in energetics and relative stabilities of these radical isomers are of interest from the perspective of fundamental physical organic chemistry and aid in understanding their behavior and reactivity in interstellar and combustion environments. Additionally, spectroscopic characterization of these species in the laboratory is essential for their potential identification in astrochemical data.

scholarly journals Highly-Excited State Properties of Cumulenone Chlorides in the Vacuum-Ultraviolet

2020 ◽  
Author(s):  
Quynh Nguyen ◽  
William Peters ◽  
Ryan Fortenberry
Keyword(s):  
Excited States ◽  
Vacuum Ultraviolet ◽  
Lone Pair ◽  
Carbon Chain ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Chain Elongation ◽  
Electronic Excitations ◽  
Quantum Chemical Analysis ◽  
Poten Tials

<div><div><div><p>Recent observations of chloromethane in interstellar environments suggest that other organohalo- gens, which are known to be critically important in Earth′s atmosphere, may also be of significance beyond our own terrestrial veil. This raises the question of how such molecules behave under extreme conditions such as when exposed to vacuum ultraviolet (VUV) radiation. VUV photons promote molecules to highly excited states that fragment in non-statistical patterns controlled by the initial femtosecond dynamics. A detailed understanding of VUV-driven photochemistry in complex organic molecules that consist of more than one functional group is a particularly challenging task. This quantum chemical analysis reports the electronic states and ionization potentials up to the VUV range (6 - 11 eV) of the chlorine-substituted cumulenone series molecules. The valence and Rydberg properties of lone-pair terminated, π-conjugated systems are explored for their potential resonance with lone pairs from elsewhere in the system. The carbon chain elongation within the family ClHCnO, where n=1-4, influences the electronic excitations, associated wavefunctions, and ionization poten- tials of the molecules. The predicted geometries and ionization potentials are in good agreement with the available experimental photoelectron spectra for formyl chloride and chloroketene, n=1-2. Furthermore, comparison between the regular cumulenone species and the corresponding chlorinated derivatives exhibit similar behaviors especially for n=3, where the allene backbone in propadienone chloride is severely bent. Most notably for the excited states is that the Rydberg character becomes more dominant as the energy increases, with some retaining valence characters.</p></div></div></div>

scholarly journals Good Vibrations: Calculating Excited State Frequencies Using Ground State Self-Consistent Field Models

2021 ◽  
Author(s):  
Ali Abou Taka ◽  
Hector Corzo ◽  
Aurora Pribram-Jones ◽  
Hrant Hratchian
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Photoelectron Spectra ◽  
Configuration Interaction Method ◽  
Functional Theory ◽  
Spin Contamination ◽  
Purification Technique ◽  
Self Consistent Field ◽  
Efficient Exploration ◽  
Scf Calculations

△SCF methods have proven to be reliable computational tools for the assignment and interpretation of photoelectron spectra of isolated molecules. These results have increased the interest in △SCF techniques for electronic excited states based on improved algorithms that prevent convergence to ground states. In this work, one of these △SCF improved algorithms is studied to demonstrate its ability to explore the molecular properties for excited states. Results from △SCF calculations for a set of representative molecules are compared with results obtained using time-dependent density functional theory and single substitution configuration interaction method. For the △SCF calculations, the efficacy of a spin-purification technique is explored to remedy some of the spin-contamination presented in some of the SCF solutions. The obtained results suggest that the proposed projection-based SCF scheme, in many cases, alleviates the spin--contamination present in the SCF single determinants, and provides a computational alternative for the efficient exploration of the vibrational properties of excited states molecules.

scholarly journals Dyson Orbitals within the fc-CVS-EOM-CCSD Framework: Theory and Application to X-ray Photoelectron Spectroscopy of Ground and Excited States

2019 ◽  
Author(s):  
Marta L. Vidal ◽  
Anna Krylov ◽  
Sonia Coriani
Keyword(s):  
Excited States ◽  
Ground State ◽  
Photoelectron Spectroscopy ◽  
Equation Of Motion ◽  
Photoelectron Spectra ◽  
Coupled Cluster ◽  
Time Resolved ◽  
X Ray ◽  
Target States

We report on the implementation of Dyson orbitals within the recently introduced frozen-core (fc) core-valence separated (CVS) equation-of-motion (EOM) coupled-cluster singles and doubles (CCSD) method, which enables efficient and reliable characterization of core-level states. The ionization potential (IP) variant of fc-CVS-EOM-CCSD, in which the EOM target states have one electron less than the reference, gives access to core-ionized states thus enabling modeling of<br><div>X-ray photoelectron spectra (XPS) and its time-resolved variant (TR-XPS). Dyson orbitals are reduced quantities that can be interpreted as correlated states of the ejected/attached electron; they enter the expressions of various experimentally relevant quantities. In the context of photoelectron spectroscopy, Dyson orbitals can be used to estimate the strengths of photoionization transitions. We illustrate the utility of Dyson orbitals and fc-CVS-EOM-IP-CCSD by calculating XPS of the ground state of adenine and TR-XPS of the excited states of uracil.</div>

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