scholarly journals Combined Experimental and Theoretical Study on Photoionization Cross Sections of Benzonitrile and o/m/p-Cyanotoluene

2021 ◽  
Author(s):  
Jiabin Huang ◽  
Can Huang ◽  
Xiaoqing Wu ◽  
Qifeng Hou ◽  
Guangjun Tian ◽  
...  
Keyword(s):  
Cross Sections ◽  
Aromatic Compounds ◽  
Vacuum Ultraviolet ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Decomposition Analysis ◽  
Interstellar Space ◽  
Hartree Fock ◽  
Photoionization Mass Spectrometry ◽  
Key Species

Toluene is one of the most abundant aromatic compounds in the atmosphere of Titan, and CN group has been regarded as an indicator for observing aromatic compounds in interstellar medium due to the large dipole moments resulted from the CN substituents. In the present work, the photoionization cross-sections (PICS) of benzonitrile and o/m/p-cyanotoluene, which are the products of CN + toluene were obtained at the photon energy ranging from ionization threshold to 14 eV combining experimental and theoretical methods. The synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was employed, and theoretical calculations based on the frozen-core Hartree-Fock approximation and Franck-Condon simulations were carried out to cross-verify the measurements. In addition, the generalized charge decomposition analysis was used to investigate the characteristics of ionized molecular orbitals. Our results are valuable for quantifying these key species (especially by the SVUV-PIMS technique) and estimating related parameters such as dissociation rates in interstellar space.

scholarly journals Combined Experimental and Theoretical Study on Photoionization Cross Sections of Benzonitrile and o/m/p-Cyanotoluene

2021 ◽  
Author(s):  
Jiabin Huang ◽  
Can Huang ◽  
Xiaoqing Wu ◽  
Qifeng Hou ◽  
Guangjun Tian ◽  
...  
Keyword(s):  
Cross Sections ◽  
Aromatic Compounds ◽  
Vacuum Ultraviolet ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Decomposition Analysis ◽  
Interstellar Space ◽  
Hartree Fock ◽  
Photoionization Mass Spectrometry ◽  
Key Species

Toluene is one of the most abundant aromatic compounds in the atmosphere of Titan, and CN group has been regarded as an indicator for observing aromatic compounds in interstellar medium due to the large dipole moments resulted from the CN substituents. In the present work, the photoionization cross-sections (PICS) of benzonitrile and o/m/p-cyanotoluene, which are the products of CN + toluene were obtained at the photon energy ranging from ionization threshold to 14 eV combining experimental and theoretical methods. The synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was employed, and theoretical calculations based on the frozen-core Hartree-Fock approximation and Franck-Condon simulations were carried out to cross-verify the measurements. In addition, the generalized charge decomposition analysis was used to investigate the characteristics of ionized molecular orbitals. Our results are valuable for quantifying these key species (especially by the SVUV-PIMS technique) and estimating related parameters such as dissociation rates in interstellar space.

Vacuum ultraviolet photochemistry of the conformers of the ethyl peroxy radical

2021 ◽  
Vol 23 (38) ◽  
pp. 22096-22102
Author(s):  
Zuoying Wen ◽  
Xiaoxiao Lin ◽  
Xiaofeng Tang ◽  
Bo Long ◽  
Chengcheng Wang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Vacuum Ultraviolet ◽  
Theoretical Calculations ◽  
Peroxy Radical ◽  
Photoionization Mass Spectrometry ◽  
Condon Factors ◽  
Vuv Photoionization ◽  
Franck Condon

C2H5O2 plus its gauche and trans conformers are studied using synchrotron-based VUV photoionization mass spectrometry and theoretical calculations, and it is found that the gauche conformer has favorable Franck–Condon factors in photoionization.

Accuracy Assessment of the ROHF-CCSD(T) Calculationsof Dipole Moments of Small Radicals

1998 ◽  
Vol 63 (9) ◽  
pp. 1409-1430 ◽  
Author(s):  
Miroslav Urban ◽  
Pavel Neogrády ◽  
Juraj Raab ◽  
Geerd H. F. Diercksen
Keyword(s):  
Large Deviation ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Accuracy Assessment ◽  
Open Shell ◽  
Basis Set ◽  
Coupled Cluster ◽  
Hartree Fock ◽  
Experimental Values

Dipole moments of a series of radicals, OH, NO, NS, SF, SO, PO, ClO, CN, LiO, NO2, and ClO2 were calculated by the Coupled Cluster CCSD(T) method with the single determinant restricted open shell Hartree-Fock (ROHF) reference. For all molecules theoretical dipole moments were carefully compared to experimental values. The size and the quality of the basis set were systematically improved. Spin adaptation in the ROHF-CCSD(T) method, largest single and double excitation amplitudes and the T1 diagnostics were considered as indicators in the quality assessment of calculated dipole moments. For most molecules the accuracy within 0.01-0.03 D was readily obtained. For ClO and CN the spin adaptation was necessary - its contribution was as large as 0.03-0.045 D. Large deviation from experiment is observed for OH in its A2Σ+ excited state (0.135 D) and especially for LiO in its 2Π ground state (0.22 D). No indication of the failure of theoretical calculations was found which leads to the conclusion that, even if there is still a space for the improvement of theoretical calculations, experimental values should be reconsidered.

The absolute photoionization cross sections of helium, neon, argon and krypton in the extreme vacuum ultraviolet region of the spectrum

1976 ◽  
Vol 349 (1658) ◽  
pp. 397-421 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Vacuum Ultraviolet ◽  
Theoretical Calculations ◽  
Critical Evaluation ◽  
Inert Gases ◽  
Ultraviolet Region ◽  
Section Data ◽  
Wide Range ◽  
Helium Neon

An experiment has been set up at the Daresbury Synchrotron Radiation Facility to make absolute absorption cross section measurements over a wide range of photon energies. New data are reported for helium, neon, argon and krypton over the range 340-40 Å which are believed to be reliable to ± 5%. A critical evaluation of published cross section data has been carried out to produce best value data from the ionization thresholds throughout the vacuum ultraviolet and X-ray region. Agreement with theoretical calculations on helium is demonstrated to be within ± 2-3% from threshold down to the double ionization threshold at 79 eV. Comparison with recent calculations of photoionization cross sections has shown that the effect of electron correlations is significant for the heavier inert gases. Contrary to previous claims, the position of the M shell maximum in krypton is located at 184 + 10 eV in good agreement with r. p. a. e. calculations. Oscillator strength sum rules have been examined and their moments calculated. Discrepancies developing towards the heavier inert gases suggests a decrease in polarizabilities and other atomic factors from those predicted by Hartree-Fock calculations.

scholarly journals He2+ Impact Single Ionization Cross Sections of Fe Atom

2020 ◽  
Vol 6 (2) ◽  
pp. 127-133
Author(s):  
S. P. Gupta ◽  
K. Yadav ◽  
R. Khanal ◽  
L. K. Jha
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Impact Energy ◽  
Theoretical Calculations ◽  
Ionization Cross ◽  
Single Ionization ◽  
Hartree Fock ◽  
Ionization Cross Sections ◽  
Binary Encounter Approximation ◽  
The Given

Binary encounter approximation has been used for theoretical calculations of alpha particle (He2+) impact single ionization cross sections of iron atom at ground state in the energy range of 35 to 360 keV/amu. The cross sections for energy transfer given by Vriens’ and quantum mechanical Hartree-Fock velocity distributions for target electron have been used in the calculation. The contributions in total single ionization cross sections from 4s and 3d subshells are observed to be higher than from 3p, and the contributions from 4s decreases with increase of impact energy whereas the contribution from 3d increases. The total single ionization cross sections decrease gradually with the increase of impact energy similar to experimental results which implies that our results are in satisfactory agreement with the experimental data in the given energy range.

Theoretical Investigation of the Second and Third Order Nonlinear Optical Properties of Some Fused Heterocyclic Aromatic Compounds

1999 ◽  
Vol 579 ◽  
Author(s):  
Mamoun M. Bader
Keyword(s):  
Optical Properties ◽  
Aromatic Compounds ◽  
Nonlinear Optical ◽  
Dipole Moments ◽  
Ring System ◽  
Basis Set ◽  
Third Order ◽  
First Order ◽  
Hartree Fock ◽  
Extended Basis

ABSTRACTWe report herein the results of coupled perturbed Hartree-Fock (CPHF) ab initio extended basis set calculations on the geometric structures, dipole moments, static first-order (α), second-order (β), and third-order polarizabilities (λ) of a series of fused heterocyclic aromatic compounds based on quinoline. The effects of the presence/absence of the heteroatom as well as the introduction of other substituents at various positions in the ring system on these molecular properties are described. The effect of the presence of N-oxide is also examined. Suggestions for the design of heterocyclic systems with enhanced polarizabilities are made.

scholarly journals Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations

2021 ◽  
Vol 22 (12) ◽  
pp. 6460
Author(s):  
Mónica Mendes ◽  
Fábris Kossoski ◽  
Ana I. Lozano ◽  
João Pereira-da-Silva ◽  
Rodrigo Rodrigues ◽  
...  
Keyword(s):  
Absorption Band ◽  
Cross Sections ◽  
Density Functional ◽  
Vacuum Ultraviolet ◽  
Theoretical Calculations ◽  
Broad Band ◽  
Rydberg States ◽  
Detailed Comparison ◽  
Absorption Data ◽  
Franck Condon

We report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculations performed through the nuclear ensemble approach in combination with time-dependent density functional theory, along with additional Franck–Condon Herzberg–Teller calculations for the first absorption band (3.7–4.6 eV). The cross sections of both bromopyrimidines are very similar below 7.3 eV, deviating more substantially from each other at higher energies. In the 7.3–9.0 eV range where the maximum cross-section is found, a single and broad band is observed for 5-bromopyrimidine, while more discernible features appear in the case of 2-bromopyrimidine. Several π* ← π transitions account for the most intense bands, while weaker ones are assigned to transitions involving the nitrogen and bromine lone pairs, the antibonding σ*Br orbital, and the lower-lying Rydberg states. A detailed comparison with the available photo-absorption data of bromobenzene is also reported. We have found significant differences regarding the main absorption band, which is more peaked in bromobenzene, becoming broader and shifting to higher energies in both bromopyrimidines. In addition, there is a significant suppression of vibrational structures and of Rydberg states in the pair of isomers, most noticeably for 2-bromopyrimidine.

Cross sections for d-3H neutron interactions with samarium isotopes

2016 ◽  
Vol 104 (8) ◽  
Author(s):  
Junhua Luo ◽  
Chunlei Wu ◽  
Li Jiang ◽  
Long He
Keyword(s):  
Experimental Data ◽  
Neutron Flux ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Nuclear Model ◽  
Activation Technique ◽  
Incident Neutron ◽  
Reaction Threshold ◽  
Talys 1.6 ◽  
The Cross

Abstract:The cross sections for (n,x) reactions on samarium isotopes were measured at (d-T) neutron energies of 13.5 and 14.8 MeV with the activation technique. Samples were activated along with Nb and Al monitor foils to determine the incident neutron flux. Theoretical calculations of excitation functions were performed using the nuclear model codes TALYS-1.6 and EMPIRE-3.2 Malta with default parameters, at neutron energies varying from the reaction threshold to 20 MeV. The results were discussed and compared with experimental data found in the literature. At neutron energies 13.5 and 14.8 MeV, the cross sections of the

scholarly journals The Potential of Vacuum Ultraviolet Photoionization Mass Spectrometry in Monitoring Photofragmentation of Organometallics

1993 ◽  
Vol 13 (2) ◽  
pp. 113-119 ◽  
Author(s):  
S. Georgiou ◽  
E. Mastoraki ◽  
E. Raptakis ◽  
Z. Xenidi
Keyword(s):  
Molecular Beam ◽  
Vacuum Ultraviolet ◽  
Impact Ionization ◽  
Microwave Discharge ◽  
Fragmentation Pattern ◽  
Photoionization Mass Spectrometry ◽  
Vuv Photoionization ◽  
Ionic Fragmentation ◽  
Deposition Processes ◽  
Fragmentation Patterns

The paper examines the potential of vacuum ultraviolet (VUV) photoionization mass spectroscopy in probing the fragmentation of organometallics in molecular-beam studies and laser-assisted deposition processes. To this end, the ionic fragmentation pattern of few common organometallics, namely metallocenes and carbonyls, is examined at selected VUV wavelengths, produced by microwave-discharge resonance atomic lamps. Discussion of the recorded spectra in terms of the electronic structure of the compounds indicates lack of dynamical bias in the VUV photoionization/fragmentation of metal complexes. Excitation with VUV light results in simpler ionic fragmentation patterns than what observed with electron-impact ionization, thereby enabling accurate monitoring of the excimer-laser photodissociation of organometallics. Finally, the intensity of the VUV ionic signal appears to be adequate for molecular-beam studies. An illustrative example is provided for the study of the 248nm-induced photodesorption of Mo(CO)6 from cryogenic films.

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