共查询到20条相似文献,搜索用时 15 毫秒
1.
V. V. Afrosimov L. A. Baranova A. A. Basalaev M. N. Panov O. V. Smirnov A. V. Tulub 《Technical Physics》2010,55(3):357-366
The subject of investigation is the fragmentation of variously charged molecular ions arising in col-lisions of several kiloelectronvolt
H+, He2+, and Ar6+ ions with molecules of the simplest alkanes (from methane to butane). Using the method of time-of-flight mass spectrometry,
the formation cross sections of dissociation-induced fragment ions are measured. The dissociation takes place when an incident
ion captures an electron from a methane, ethane, or propane molecule. The role of additional ionization of the molecule, which
accompanies the electron capture by the incident ion, is elucidated. The kinetic energy spectrum for protons resulting from
the fragmentation of multiply charged alkane ions is determined. The most plausible kinetic energies of protons depending
on the degree of ionization and molecule size fall into the range 1–25 eV. It is shown that, when the molecule loses several
electrons, the kinetic energies of protons are governed by Coulomb interaction between all fragment ions and are determined
by their flying apart from the relative spatial arrangement of corresponding atoms in a parent molecule. 相似文献
2.
S. A. Pshenichnyuk A. V. Kukhto I. N. Kukhto N. L. Asfandiarov 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(6):1014-1027
Bound states of electrons with electroactive aromatic molecules, promising for use in molecular electronics, are studied employing
electron attachment spectroscopy Anions are produced in the gas phase through the capture of electrons with energies of up
to 15 eV by molecules via the resonance mechanism. The possible pathways of fragmentation of molecular anions and the times
of electron retention by the test molecules at various incident electron energies are measured. The resonance states identified
are interpreted with the help of quantum-chemical calculations. The possibility of applying the results obtained to molecular
electronics is discussed. 相似文献
3.
B. Coupier B. Farizon M. Farizon M.J. Gaillard F. Gobet N.V. de Castro Faria G. Jalbert S. Ouaskit M. Carré B. Gstir G. Hanel S. Denifl L. Feketeova P. Scheier T.D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):459-468
Ionization and fragmentation of water and uracil molecules was studied both by electron and proton impact. A special coincidence
technique allows on an event by event basis the investigation of product ions formed upon the collision of protons with neutral
molecules including the identification of the charge state of the projectile. This enables the characterization of the ionization
processes occurring, i.e. direct ionization, single electron capture or double electron capture for 0, 1 or 2 electrons that are transferred from the
target to the projectile, respectively. For uracil the fragmentation patterns obtained by electron and proton impact ionization
reveal close similarities and indicate a comparable amount of excitation for the two different ionization mechanisms at high
enough projectile energies.
Received 25 February 2002 Published online 13 September 2002 相似文献
4.
V. V. Afrosimov A. A. Basalaev V. V. Kuz’michev M. N. Panov O. V. Smirnov 《Technical Physics》2016,61(3):342-348
The relative cross sections of elementary processes occurring in single collisions of tryptophan molecules in the gaseous phase with He2+ ions with energy 4 keV/u are measured using time-of-flight mass spectrometry for studying the mechanism of radiation damage of amino acid molecules. The fragmentation channels for intermediate singly and doubly charged tryptophan molecular ions formed during one-electron capture, two-electron capture, and electron capture with ionization are investigated. Significant difference is observed in the mass spectra of fragmentation of intermediate doubly charged ions formed during the capture with ionization and double capture, which is associated with different energies of excitation of {C11H12N2O2}2+* ions. 相似文献
5.
Rentenier A Ruiz LF Díaz-Tendero S Zarour B Moretto-Capelle P Bordenave-Montesquieu D Bordenave-Montesquieu A Hervieux PA Alcamí M Politis MF Hanssen J Martín F 《Physical review letters》2008,100(18):183401
We have determined absolute charge transfer and fragmentation cross sections in He2++C60 collisions in the impact-energy range 0.1-250 keV by using a combined experimental and theoretical approach. We have found that the cross sections for the formation of He+ and He0 are comparable in magnitude, which cannot be explained by the sole contribution of pure single and double electron capture but also by contribution of transfer-ionization processes that are important even at low impact energies. The results show that multifragmentation is important only at impact energies larger than 40 keV; at lower energies, sequential C2 evaporation is the dominant process. 相似文献
6.
In this paper Monte Carlo simulations of a dissociative electron transfer reaction in solution have been performed in order to test to what extent the deviation of Marcus' relationship for this kind of reactions can be attributed to the features of the solute internal potential energy. It is shown that Marcus' equation does not apply to this kind of dissociative electron transfer processes if the ab initio solute internal potential energies are used. Conversely, if a Morse curve and its repulsive part are employed to describe the solute internal potential energies, Marcus' relationship is recovered. Then, the problem is reduced to what extent the ab initio solute internal potential energies can be represented by Morse curves. 相似文献
7.
The cross sections of dissociative excitation of 46 transitions from cobalt atom even sextet levels in collisions of electrons with CoCl2 molecules were measured at an exciting electron energy of 100 eV. The dissociative and direct CoI excitation cross sections were compared. The results were used to calculate the total cross sections of dissociative excitation of CoI levels at an electron energy of 100 eV. Possible reaction channels at low electron energies are discussed. 相似文献
8.
We describe an experiment to establish the chemical stability and measure the binding energies of compounds containing positronium atoms. The method consists of crossing a monoenergetic beam of low energy (1–25 eV) positrons with a supersonic adiabatic expansion molecular beam, and, after a dissociative attachment reaction takes place, detecting the resulting ¡gnature ion while measuring its kinetic energy. Except for the use of a positron beam instead of an electron beam, this is similar to electron impact MS/IKES (mass spectrometry/ion kinetic energy spectrometry). The start signal for the IKES measurement is provided by the remoderation of the positron beam. Among the benefits of the proposed research are the study of: (1) a new class of resonances, those involving temporarily bound positrons to molecules in excited electronic states; and (2) the surprising sub-threshold fragmentation observed by Surko and Hulett in positron-molecule scattering. 相似文献
9.
A detailed theoretical study is carried out for electron interactions with formyl radical (HCO) with incident energies ranging from 0.01 to 5000 eV. This wide range of energy has allowed us to investigate a variety of processes and report data on vertical electronic excitation energies, dissociative electron attachment (DEA) and total cross-section along with scattering rate coefficients. We observed Ramsaur–Townsend minimum at 0.59 and 0.74 eV using DZP and cc-pDVZ basis sets, respectively. HCO has large number of low-lying excited states and the present study finds an overall good agreement with earlier reported data. In order to compute total cross-section, we have employed ab initio R-matrix method (0.01 to ~ 20 eV) and the spherical complex optical potential method (~ 10 to 5000 eV) employing static-exchange plus polarisation potential. The R-matrix calculations are performed using a close coupling method with the aid of 21 target states, 1191 configuration state functions and 195 channels. The DEA cross-sections of fragmentation of H?, excitation cross- sections and scattering rate coefficients are reported for the first time. Total cross section presented here will provide a reference data set over an extensive impact energy range. 相似文献
10.
V. V. Afrosimov A. A. Basalaev V. P. Belik Yu. V. Maidl’ M. N. Panov O. V. Smirnov 《Technical Physics》1998,43(4):358-360
The cross sections for the elementary processes involving a change of the charge states of both particles during the interaction
of He2+ ions with fullerene molecules are for the first time measured over a broad energy range of electron-volt energies. It is
found that processes involving the capture of one or two electrons by the He2+ ions are accompanied by additional ionization of the fullerene and that the collisional contribution of the transfer-ionization
processes increases with increasing velocity. Single-electron capture is rarely accompanied by fragmentation of the fullerene.
Double-electron capture leads, with a higher probability, to fragmentation with the formation of several light charged fragments
and, with a smaller probability, to fragmentation with the formation of a heavy charged fragment containing an even number
of carbon atoms and light fragments in an uncharged state.
Zh. Tekh. Fiz. 68, 12–14 (April 1998) 相似文献
11.
12.
The dissociative excitation of singlet and quintet nickel atom states in e-NiBr2 collisions was studied by the method of extended intersecting beams. Optical excitation functions over the electron energy
range 0–100 eV were recorded for most of the spectral lines observed. Possible dissociative excitation channels at low electron
energies were discussed. The cross sections of dissociative and direct excitations and dissociative excitations of the NiBr2 and NiCl2 molecules were compared. 相似文献
13.
We study the control of dissociation of the hydrogen molecular ion and its isotopes exposed to two ultrashort laser pulses by solving the time-dependent Schr?dinger equation. While the first ultraviolet pulse is used to excite the electron wave packet on the dissociative 2psigma{u} state, a second time-delayed near-infrared pulse steers the electron between the nuclei. Our results show that by adjusting the time delay between the pulses and the carrier-envelope phase of the near-infrared pulse, a high degree of control over the electron localization on one of the dissociating nuclei can be achieved (in about 85% of all fragmentation events). The results demonstrate that current (sub-)femtosecond technology can provide a control over both electron excitation and localization in the fragmentation of molecules. 相似文献
14.
The transition rates for unbound muons to be captured into atomic bound states are calculated as functions of (1) incident muon center-of-mass energy, (2) muon principal quantum number n, and (3) muon (final) angular momentum l, for the hydrogen, helium, and lithium atoms. These rates reflect differences in electron binding energies. At muon energies of several hundred electron volts, lithium K-shell electrons are more likely to be ejected than the L-shell electron, while this behavior is reversed for energies ? 10 eV. However, in each case when the capture rate is folded with a muon stopping power function, the result is that more than half of the unbound muons are absorbed above 75 eV. Implications for experiments which look at muon transfer processes are noted. 相似文献
15.
M. Vogler 《Zeitschrift für Physik A Hadrons and Nuclei》1978,288(1):7-10
The velocity distributions of H-H fragment pairs arising from dissociative collisions of 10keV H 2 + ions incident on H2, He, and Ar were measured using a flight-time-difference method. The H 2 + ions were produced in an electron impact ion source at two different electron energies, at 100eV and 18eV. The influence of the electron energy on the fragment velocity distributions is studied. Conclusions are drawn on the processes which lead to the formation of neutral fragment pairs. Electron capture into the repulsive b3 Σ u + state of H2 plays a dominant role. 相似文献
16.
J. de Vries R. Hoekstra R. Morgenstern T. Schlathölter 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):161-164
Ionization and fragmentation of the DNA base thymine upon
interaction with keV Cq+ ions
(q
= 1 -
6) has been studied. By means of time-of-flight
spectrometry of two or more thymine fragments in coincidence
with an ejected electron we could investigate particular
dissociation channels by means of their associated
kinetic-energy-release. The fragmentation dynamics are strongly
influenced by the Cq+ charge state:
for low q values mainly
fragmentation due to direct collisions is observed. With
increasing q, electron capture
becomes more important. For larger q we could identify several Coulomb
explosion channels, leading to very energetic fragments. 相似文献
17.
We use dibutyl phosphate to simulate the behavior of the phosphate group in DNA towards the attack of low energy electrons. We find that the compound undergoes effective dissociative electron attachment within a low energy resonant feature at 1 eV and a further resonance peaking at 8 eV. The dissociative electron attachment (DEA) reactions are associated with the direct cleavage of the C-O and the P-O bond but also the excision of the PO-, PO3-, H2PO3- units. For the phosphate group coupled in the DNA network these reactions represent single strand breaks. We hence propose that the most direct mechanism of single strand breaks occurring in DNA at subexcitation energies (< 4 eV) is due to DEA directly to the phosphate group. 相似文献
18.
The dissociative excitation of doublet and octet levels of the manganese atom in collisions of slow electrons with manganese
diiodide molecules is studied. At the exciting electron energy of 100 eV, the excitation cross sections for 28 and 12 transitions,
respectively, from doublet and octet states of manganese atom are measured. In the exciting electron energy range of 0–100
eV, six optical excitation functions are recorded. The possible channels of the formation of excited manganese atoms at low
electron energies are discussed. 相似文献
19.
Asfandiarov N. L. Pshenichnyuk S. A. Rakhmeev R. G. Lachinov A. N. Kraikin V. A. 《Technical Physics》2018,63(7):1054-1059
Technical Physics - Molecules of diphenylphthalide and 3,3-diphenylphthalide-4′,4′-dicarbonic acid have been studied using the method of dissociative electron capture negative ion mass... 相似文献
20.
H. D. Flosadóttir B. Ómarsson I. Bald O. Ingólfsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):13
Here we review recent studies on the metastable fragmentation of individual DNA and RNA building blocks and their compositions
using matrix assisted laser desorption/ionization mass spectrometry (MALDI). To compare the fragmentation channels of small
DNA components with larger compositions we have studied the metastable fragmentation of the deprotonated nucleobases, ribose,
ribose-monophoshates, the nucleosides, the nucleoside 5′-monophosphates and selected oligonucleotides. Both previously published
and unpublished data are reported. To gain a comprehensive picture of the fragmentation of individual components, metastable
fragmentation of native components are in many cases compared to chemically modified components and isotopic labelling is
used to unambiguously identify fragments. Furthermore, to shed light on the underlying fragmentation mechanisms we complement
the experimental studies with classical dynamics simulations of the fragmentation of selected compounds. For the DNA and RNA
components where dissociative electron attachment studies have been conducted we compare these to the metastable fragmentation
channels observed here. 相似文献