scholarly journals Determination of Electron Affinity on the Base of Experimentally Measured Lifetime of Negative Molecular Ions of Coumarin Derivatives

2020 ◽  
pp. 45-59
Author(s):  
Mansaf Tayupov ◽  
Rustam Rakhmeev ◽  
Nail Asfandiarov ◽  
Stanislav Pshenichnyuk
Keyword(s):  
Electron Affinity ◽  
Density Functional ◽  
Negative Ions ◽  
Density Functional Theory Calculations ◽  
Molecular Ions ◽  
Negative Ion ◽  
Decay Channels ◽  
Negative Ion Mass Spectrometry ◽  
Mean Lifetime ◽  
Total Energies

Resonance attachment of low-energy (0–15 eV) electrons to molecules of 4.7- and 6.7-dihydroxycoumarin was investigated by means of negative ion mass spectrometry. These natural compounds possess biological activity associated with antioxidant and bactericidal properties. The most probable structures of the fragment negative ions ([M – H]–, [M – 2H]–, [M – СО]–, [M – СОH]–, [M – СООH]– etc.) were predicted by means of analysis of decay channels for the molecular negative ions using the results of density functional theory calculations. Mean lifetime for molecular negative ions of 4.7-dihydroxycoumarin relative to electron autodetachment was measured. The adiabatic electron affinity (EAa) was estimated in the framework of the Arrhenius approximation. It was found that EAa values calculated at B3LYP/6-31+G(d) level with minimal addition of diffuse functions as a difference between the total energies of a neutral molecule and its radical anion correlate with experimental EAa values.

First-Principles Analysis on Interaction between Dopant (Ga, Sb) and Contamination Metal Atoms in Ge Crystals

2013 ◽  
Vol 205-206 ◽  
pp. 417-421
Author(s):  
Tatsunori Yamato ◽  
Koji Sueoka ◽  
Takahiro Maeta
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Functional Theory ◽  
Substitutional Site ◽  
Metal Impurities ◽  
Metal Atoms ◽  
Total Energies ◽  
Group 3

The lowest energetic configurations of metal impurities in 4throw (Sc - Zn), 5throw (Y - Cd) and 6throw (Hf - Hg) elements in Ge crystals were determined with density functional theory calculations. It was found that the substitutional site is the lowest energetic configuration for most of the calculated metals in Ge. The most stable configurations of dopant (Ga, Sb) - metal complexes in Ge crystals were also investigated. Following results were obtained. (1) For Ga dopant, 1st neighbor T-site is the most stable for metals in group 3 to 7 elements while substitutional site next to Ga atom is the most stable for metals in group 8 to 12 elements. (2) For Sb dopant, substitutional site next to Sb atom is the most stable for all calculated metals. Binding energies of the interstitial metalMiwith the substitutional dopantDswere obtained by the calculated total energies. The calculated results for Ge were compared with those for Si.

Negative Ionen durch Elektronenstoß aus organischen Nitroverbindungen, Äthylnitrit und Äthylnitrat

1967 ◽  
Vol 22 (5) ◽  
pp. 700-704
Author(s):  
K. Jäger ◽  
A. Henglein
Keyword(s):  
Electron Impact ◽  
Negative Ions ◽  
Molecular Ions ◽  
Ion Source ◽  
Negative Ion ◽  
Electron Affinities ◽  
Low Intensity ◽  
Ion Molecule Reactions ◽  
Fragment Ions ◽  
Product Ions

Negative ion formation by electron impact has been studied in nitromethane, nitroethane, nitrobenzene, tetranitromethane, ethylnitrite and ethylnitrate. Appearance potentials, ionization efficiency curves and kinetic energies of negative ions were measured by using a Fox ion source. The electron affinities of C2H5O and of C (NO2)3 are discussed as well as the energetics of processes which yield NO2-. The electron capture in nitrobenzene and tetranitromethane leads to molecular ions [C6H5NO2~ in high, C (NO2)4 in very low intensity] besides many fragment ions. A number of product ions from negative ion-molecule reactions has also been found.

Mass Spectrometry of Cyclopentadienylideneketene: Differentiation of Isomeric Ion Structures by Means of Ion/Molecule Reactions

2012 ◽  
Vol 65 (12) ◽  
pp. 1655 ◽  
Author(s):  
Pascal Gerbaux ◽  
Curt Wentrup
Keyword(s):  
Mass Spectrometry ◽  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
Molecular Ions ◽  
Functional Theory ◽  
Clear Cut ◽  
Ion Molecule Reactions ◽  
Hybrid Mass Spectrometer

The nature of the m/z 104 ions formed by loss of CO2 or Ph-O-NCO from the molecular ions of phthalic anhydride, N-phenoxyphthalimide, and N-phenoxyisophthalimide was investigated by means of ion/molecule reactions with acetone. This allows a clear-cut differentiation of the so-obtained ions from the isomeric molecular ions of cyclopentadienylideneketene. The different intrinsic chemical reactivities of ionized cyclopentadienylideneketene and its distonoid isomer towards neutral acetone were investigated on a large-scale hybrid mass spectrometer and confirmed by density functional theory calculations.

scholarly journals A novel rocket borne ion mass spectrometer with large mass range: instrument description and first flight results

2020 ◽  
Author(s):  
Joan Stude ◽  
Heinfried Aufmhoff ◽  
Hans Schlager ◽  
Markus Rapp ◽  
Frank Arnold ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Negative Ions ◽  
Mass Range ◽  
Large Mass ◽  
Molecular Ions ◽  
Negative Ion ◽  
Cluster Ions ◽  
The Arctic ◽  
Atmospheric Species ◽  
Smoke Particles

Abstract. We present a novel rocket borne ion mass spectrometer ROMARA (ROcket borne MAss spectrometer for Research in the Atmosphere) for measurements of atmospheric positive and negative ions (atomic, molecular and cluster ions) and positively and negatively charged meteor smoke particles. Our ROMARA instrument has, compared to previous rocket borne ion mass spectrometers, a markedly larger mass range of up to m/z 2000 and a larger sensitivity, particularly for meteor smoke particle detection. Mayor objectives of this first ROMARA flight included: a functional test of the ROMARA instrument, measurements between 55 km and 121 km in the mass range of atmospheric positive and negative ions, a first attempt to conduct mass spectrometric measurements in the mass range of meteor smoke particles with mass to charge ratios up to m/z 2000, and measurements inside a polar mesospheric winter echo layer as detected by ground based radar. Our ROMARA measurements took place on the Arctic island of Andøya/Norway around noon in April 2018 and represented an integral part of the PMWE rocket campaign. During the rocket flight, ROMARA was operated in a measurement mode, offering maximum sensitivity and the ability to qualitatively detect total ion signatures even beyond its mass resolving mass range. On this first ROMARA flight we were able to meet all of our objectives. We detected atmospheric species including positive atomic, molecular and cluster ions along with negative molecular ions up to about m/z 100. Above m/z 2000, ROMARA measured strong negative ion signatures, which are likely due to negatively charged meteor smoke particles.

scholarly journals Fullerene Negative Ions: Formation and Catalysis

2020 ◽  
Vol 21 (9) ◽  
pp. 3159
Author(s):  
Zineb Felfli ◽  
Kelvin Suggs ◽  
Nantambu Nicholas ◽  
Alfred Z. Msezane
Keyword(s):  
Transition State ◽  
Cross Sections ◽  
Water Oxidation ◽  
Density Functional ◽  
Regge Pole ◽  
Negative Ions ◽  
State Density ◽  
Negative Ion ◽  
Functional Theory ◽  
Total Cross Sections

We first explore negative-ion formation in fullerenes C44 to C136 through low-energy electron elastic scattering total cross sections calculations using our Regge-pole methodology. Then, the formed negative ions C44ˉ to C136ˉ are used to investigate the catalysis of water oxidation to peroxide and water synthesis from H2 and O2. The exploited fundamental mechanism underlying negative-ion catalysis involves hydrogen bond strength-weakening/breaking in the transition state. Density Functional Theory transition state calculations found C60ˉ optimal for both water and peroxide synthesis, C100ˉ increases the energy barrier the most, and C136ˉ the most effective catalyst in both water synthesis and oxidation to H2O2.

Studies in Negative-Ion Mass Spectrometry. XII. Electron Attachment to a Series of Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)-metal Complexes

1979 ◽  
Vol 32 (11) ◽  
pp. 2405 ◽  
Author(s):  
DR Dakternieks ◽  
IW Fraser ◽  
JL Garnett ◽  
IK Gregor
Keyword(s):  
Mass Spectra ◽  
Electron Attachment ◽  
Negative Ions ◽  
Fragmentation Pathway ◽  
Negative Ion ◽  
Metal Fluoride ◽  
Class A ◽  
Negative Ion Mass Spectrometry ◽  
Fragment Ions ◽  
Rearrangement Processes

Results of electron-attachment reactions in the gas phase as well as negative-ion mass spectra are given for a series of bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)metal(1) complexes, (ML2), with the divalent metals MgII, MnII, Co11, Nil1, Cu11 and ZnII. While molecular, [ML2]- or [ML2]-, and ligand, [L]-, ions are present in the negative-ion mass spectra, the lability of the ligand C-F and C-CF3 bonds enables rearrangement processes involving fluorine atom transfers to become significant in the decompositions of both molecular and fragment ions, particularly for the class (a) metals, for which significant yields of [MLF2] and [MLF] negative ions were obtained. Thus, the predominant fragmentation pathway for such metal-containing complexes, for which metastable peaks have been assigned, occurs in the sequence [ML2]- -(*) → (MLF2]- - (8) → [L]- or alternatively [ML2]- -(*) → (MLF2]- - (8) → [L]- with the latter fragmentation in these sequences involving the elimination of the divalent metal fluoride, MF2.

scholarly journals A novel rocket-borne ion mass spectrometer with large mass range: instrument description and first-flight results

2021 ◽  
Vol 14 (2) ◽  
pp. 983-993
Author(s):  
Joan Stude ◽  
Heinfried Aufmhoff ◽  
Hans Schlager ◽  
Markus Rapp ◽  
Frank Arnold ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Negative Ions ◽  
Mass Range ◽  
Large Mass ◽  
Molecular Ions ◽  
Negative Ion ◽  
Cluster Ions ◽  
The Arctic ◽  
Atmospheric Species ◽  
Smoke Particles

Abstract. We present a novel rocket-borne ion mass spectrometer named ROMARA (ROcket-borne MAss spectrometer for Research in the Atmosphere) for measuring atmospheric positive and negative ions (atomic, molecular and cluster ions) and positively and negatively charged meteor smoke particles. Our ROMARA instrument has, compared to previous rocket-borne ion mass spectrometers, a markedly larger mass range of up to m/z 2000 and a larger sensitivity, particularly for meteor smoke particle detection. The major objectives of this first ROMARA flight included the following: a functional test of the ROMARA instrument, measurements between 55 and 121 km in the mass range of atmospheric positive and negative ions, a first attempt to conduct mass spectrometric measurements in the mass range of meteor smoke particles with mass-to-charge ratios up to m/z 2000, and measurements inside a polar mesospheric winter echo layer as detected by ground-based radar. Our ROMARA measurements took place on the Arctic island of Andøya, Norway, at around noon in April 2018 and represented an integral part of the polar mesospheric winter radar echo (PMWE) rocket campaign. During the rocket flight, ROMARA was operated in a measurement mode, offering maximum sensitivity and the ability to qualitatively detect total ion signatures even beyond its mass-resolving mass range. On this first ROMARA flight we were able to meet all of our objectives. We detected atmospheric species including positive atomic, molecular and cluster ions along with negative molecular ions up to about m/z 100. Above m/z 2000, ROMARA measured strong negative-ion signatures, which are likely due to negatively charged meteor smoke particles.

The attachment of slow electrons in carbon dioxide

1960 ◽  
Vol 254 (1277) ◽  
pp. 229-241 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Kinetic Energy ◽  
Cross Section ◽  
Electron Affinity ◽  
Negative Ions ◽  
Negative Ion ◽  
Initial Kinetic Energy ◽  
A Value ◽  
Normal Electron ◽  
Peak Cross Section

The formation of positive and negative ions in carbon dioxide has been investigated by means of a Lozier apparatus. The negative ion process was interpreted as CO 2 + e → CO( X 1 Σ + ) + O - (2 P 0 ). The (peak) cross-section for electron attachm ent was found to be 5·07 ± 0·5 x 10 -19 cm 2 at 7·8 eV, and the ionization cross-section reached a m axim um value of 6·80 x 10 -16 cm 2 at 85 eV. Measurements of the electron affinity of oxygen by the normal electron impact method yielded a value of 1·6 ± 0·2 eV for O - ions formed with an initial kinetic energy of 1·8 eV. It is shown that this apparent value of electron affinity must be corrected, because of the initial kinetic energy of the ions and the energy spread of the source electrons, and then yields a value of 1·2 ± 0·3 eV.

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