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1.
B. Brunetti P. Candori S. Falcinelli B. Lescop G. Liuti F. Pirani F. Vecchiocattivi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):21-27
A crossed beam experiment is carried out to measure the energy of electrons
emitted in Penning ionization processes by Ne*(3P2,0)–Kr
collisions. The electron energy spectra have been measured at four different
collision energies: 0.050, 0.140, 0.190, 0.460 eV. The analysis of the
results allows the separation of spin orbit contributions both in the
entrance and in the exit channels providing the related cross-section
ratios. Some theoretical considerations have been made to clarify nature and
role of interatomic potentials driving the collisions and some general
features about the role of atomic fine structure in the Penning ionization
processes. 相似文献
2.
G. García E. Mejía-Ospino A. Guerrero I. Álvarez C. Cisneros 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):393-396
The kinetic energy release distributions (KERDs) of
C+ and O+ fragments arising from 5 keV collision-induced
dissociation (CID) of CO+ ions with helium have been measured. The
KERDs of C+ and O+ exhibit different features corresponding to the
states that participate in CID processes. We have identified groups of
dissociative and predissociative states, and compare them with theoretical
and experimental values. 相似文献
3.
F.A. Gianturco T. Mukherjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):211-218
The scattering of slow positrons from and NO molecules is treated using exact static interactions and a model potential for correlation-polarisation forces. The
quantum coupled equations for the elastic scattering are extended to vibrationally inelastic processes and the different excitation
probabilities are evaluated. Comparison with existing experiments for the NO target indicates that the present calculations
provide a realistic treatment of positron scattering below Ps formation and give computational estimates on the efficiency
of such projectiles in producing vibrationally excited molecules in the ambient gas.
Received: 23 April 1999 / Received in final form: 3 June 1999 相似文献
4.
M. Kimura L. Pichl Y. Li H.-P. Liebermann R. J. Buenker I. F. Schneider 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):85-91
The positive water and hydronium ions are of interest in a
variety of chemical and biological applications. Here we study the
steric effect in charge transfer collisions, i.e. the spatial
dependence of single electron capture, in collisions mediated by
these ions. In particular, the steric effect is demonstrated in the
O+(2D)/H2 and H+/H2O charge transfer collisions in
the energy range of 100 eV/amu to 10 keV/amu. 相似文献
5.
M.N.R. Ashfold S.R. Langford R.A. Morgan A.J. Orr-Ewing C.M. Western C.R. Scheper C.A. de Lange 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(2):189-197
Resonance enhanced multiphoton ionization (REMPI) spectroscopy, preferably linked with kinetic energy analysis of the resulting
photoelectrons (REMPI-photoelectron spectroscopy (PES)), continues to make enormous contributions to our understanding of
the spectroscopy and, in many cases, the decay dynamics of small molecules in excited (normally Rydberg) electronic states.
Here we present results of recent REMPI and REMPI-PES studies involving the ammonia molecule which provide further illustration
of some of the many opportunities offered by these techniques.
Received: 28 January 1998 / Revised: 3 April 1998 / Accepted: 15 April 1998 相似文献
6.
M. Yamazaki N. Kishimoto K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):47-57
Collisional ionization of styrene (phenylethylene), 2-vinylpyridine, and
4-vinylpyridine with metastable He*(23S) atoms were studied by means of
collision-energy/electron-energy resolved two-dimensional Penning
ionization electron spectroscopy. Collision energy dependence of partial
ionization cross-sections, which reflects the anisotropic interactions
between a He*(23S) atom and the target molecules, indicates that
attractive interaction for the out-of-plane access of a He*(23S) atom
to phenyl group is stronger than that for the out-of-plane access to vinyl
group. Moreover, it was found for vinylpyridines that the attractive
interaction around π electrons became weaker than that for styrene, and
that the attractive interaction for the in-plane access to the nitrogen atom
is stronger than that for out-of-plane π-directions. However, in
2-vinylpyridine, the hydrogen atom of vinyl group prevents a He*(23S)
atom from approaching to the nitrogen atom along in-plane directions, and
thus the attractive interactions around the nitrogen atom were shielded by
the vinyl group. The experimentally observed anisotropic interactions were
qualitatively supported with ab initio model interaction potential calculations
between a Li (He*(23S)) atom and the target molecule. Concerning with
electronic structures of investigated molecules, the assignment of Penning
ionization electron spectrum for 4-vinylpyridine was discussed on the basis
of different behavior of collision-energy dependence of partial ionization
cross-sections, and the satellite ionization band in Penning ionization
electron spectra was also reported for styrene. 相似文献
7.
H. Deutsch K. Becker T.D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):283-287
We report calculations of the electron-impact ionization cross-sections of selected dimers (homonuclear diatomic molecules)
and trimers (homonuclear triatomic molecules) using a method which relies only on macroscopic quantities in conjunction with
a “defect concept”. The empirically determined defect describes the deviation of the cluster (dimer, trimer) cross-sections
from a simple linear dependence on the cluster size. We compare the calculated cross-sections to experimental data for the
dimers S2 and F2 and the trimer O3 and we present predictions for the ionization cross-sections of Br2, I2, C2 and C3 for which no experimental data are available. Lastly, we extend the method to the calculation of ionization cross-sections
for the fullerenes C60 and C70.
Received 6 December 1999 and Received in final form 10 April 2000 相似文献
8.
L. Lammich S. Altevogt H. Buhr H. Kreckel S. Krohn M. Lange D. Strasser R. Repnow M. Grieser R. Schinke Z.-W. Qu H. Zhu D. Schwalm D. Zajfman A. Wolf 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):103-111
The fragmentation of LiH2
- anions after electron
impact was investigated at the heavy-ion storage ring TSR.
The main reaction channel was found to be electron detachment followed by a
breakup into LiH + H.
In the first ms after production of the molecular ions in a cesium
sputtering ion source, additional
contributions were observed in the Li + H2 and Li- + H2 channels,
hinting at an initial population of a short-lived state of the anion.
To gain a better understanding of the mechanisms underlying the observed
behavior of the system, ab initio calculations of relevant potential
energy surfaces were performed at selected geometries.
The experimental findings are discussed in the
light of these calculations. 相似文献
9.
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
10.
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
11.
B. Soep J.M. Mestdagh S. Sorgues J.P. Visticot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):191-203
In the TDMAE molecule (title molecule), the time evolution has been analyzed from the very initial excitation step down to
a fluorescent state, over widely different time scales. Pump probe measurements have been performed at 3 different excitation
wavelengths 400, 266 and 200 nm. The decay has been followed over the femtosecond and subnanosecond ranges with this method
and the decay of the final charge transfer state has been detected by its fluorescence emission. This allows an overview of
the complete decay mechanism. The initial relaxation pathway is interpreted in a similar way to ethylenic molecules, where
the initial wavepacket is quickly trapped in a doubly excited state Z with charge transfer character. Then the Z state decays
slowly (10-100 picoseconds) into the final state. In difference to monoalkenes the final stage of this evolution is a charge
transfer state. The decay of transient Z state to the charge transfer state is a further assessment of the partial ionic character
of the Z state. This type of molecule with low ionization potential can be viewed as a demonstrative example of the interrelation
between the charge induced forces and the deformations in excited state reaction dynamics.
Received 17 January 2001 and Received in final form 23 February 2001 相似文献
12.
13.
A. Ekers M. Głódź J. Szonert B. Bieniak K. Fronc T. Radelitski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):49-58
The results of an experimental study of population dynamics following excitation of [0pt] and [0pt] states of rubidium are reported. Excitation transfer and quenching cross-sections in collisions with ground state rubidium
atoms, and natural lifetimes have been measured. The experiment was performed in a vapour cell, using pulsed two-photon excitation
and photon counting detection. The analysis of time dependent signals was based on a rate equation model in which transitions
induced by thermal radiation have been accounted for. The measurements yielded following results: (1) [0pt] state J-mixing cross-section: [0pt] ; (2) cross-sections for [0pt] excitation transfer process: [0pt] ; (3) quenching cross-sections: [0pt] , [0pt] , [0pt] ; [0pt](4) radiative lifetimes: [0pt] ns, [0pt] ns, [0pt] ns.
Received 1st December 1998 and Received in final form 17 May 1999 相似文献
14.
K. Orlovsky V. Grushevsky A. Ekers 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):133-146
We present results of theoretical studies of the non-resonant excitation transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions
at thermal collision energies. Rb2 adiabatic molecular terms correlating with the 5S+7S, 5S+5D and 5P+5P states of separated atoms were calculated for internuclear
distances R > 20 a.u. using asymptotic approximation. Mechanisms of collisional population and quenching of the 5D state were treated
on the basis of the computed molecular terms, and the respective cross-sections were calculated. Theoretical cross-sections
are in good agreement with the experimental values at thermal collision energies ( K).
Received 13 November 1998 and Received in final form 22 November 1999 相似文献
15.
Dynamics of ionization mechanisms in relativistic collisions involving heavy and highly-charged ions
D.C. Ionescu A. Belkacem 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):301-307
The dynamics of mechanisms associated with the ionization of inner-shell electrons in relativistic collisions involving heavy
and highly-charged ions is investigated within a nonperturbative approach formulated explicitly in the time domain. The theoretical
treatment is based on the exact numerical solution of the time dependent Dirac equation for two Coulomb centers on a lattice
in momentum space. We present results for ionization in encounters between 100 MeV/u Au79+ projectile ions impinging on a hydrogen-like uranium target. By directly visualizing the collision dynamics we identify a
new ionization mechanism in which electrons are emitted from the internuclear region preferentially in the transverse direction
with respect to the projectile trajectory. A striking characteristic of this ionization mechanism is that the velocity of
the electron is higher than the projectile velocity.
Received 26 June 2001 and Received in final form 27 November 2001 相似文献
16.
L. Feng Y.-k. Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):25-30
In this paper, ion-atom and ion-ion collisions in the presence of intense laser fields are qualitatively studied by Classical
Trajectory Monte Carlo (CTMC) simulations. It is found that in contrast to the field-free collisions, the colliding ion and
the target nucleus could absorb energy from the applied laser fields when the electrons escape from the collision system.
This result is explained in terms of Coulomb explosion induced by the enhanced ionization at the so-called critical internuclear
distance. Also, the corresponding energy gain cross-sections are evaluated.
Received: 7 October 1998 / Received in final form: 28 January 1999 相似文献
17.
A. Salin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):189-192
We show that a classical Impact Parameter Method may be derived when taking fully into account the smallness of the ratio
between the electron and nuclear masses. It allows to calculate, exactly as in the quantum version, projectile scattering
and therefore recoil momenta required for the interpretation of recent measurements. We prove an additivity theorem which allows, in particular, to reduce the n-non-interacting electron problem to a set of n one-electron problems. Consequences for the interpretation of target recoil measurements are discussed.
Received 25 June 1999 相似文献
18.
E. Biémont P.-D. Dumont H.P. Garnir P. Palmeri P. Quinet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):199-204
Theoretical transition probabilities have been obtained for 54 n = 3 transitions depopulating the 3s3p
1Po, 3p2
3P, 1D, 1S, 3s3d
1D, 3D and 3p3d
3Po, 3Do, 3Fo, 1Fo, 1Do, 1Po levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes
obtained by beam-foil spectroscopy for four n = 3 levels of K7+. An excellent agreement is observed between theory and experiment for all the levels.
Received 23 January 2002 / Received in final form 23 April 2002 Published online 19 July 2002 相似文献
19.
E. De Filippo G. Lanzanò H. Rothard C. Volant A. Anzalone N. Arena M. Geraci F. Giustolisi A. Pagano 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):349-356
A rather complete experimental study of forward and backward electron velocity spectra from thin foils bombarded with ions
at constant velocity of 30 atomic units (23MeV u^-1) was performed. Three different beams ( 12C3+ , 58Ni14+ and 197Au36+ and six different targets ( 12C , 27Al , natNi , natAg , 197Au and 209Bi of approximately 90μg cm^-2 thickness were used. This procedure allowed to study the evolution of electron emission (velocity
and angular distributions) for the [projectile; target] matrix [ C , Ni , Au ; C , Al , Ni , Ag , Au , Bi ] in a wide angular
range. The projectile and target dependence of absolute cross-sections for binary encounter-, Auger- and backward-emitted
electrons are analyzed. 相似文献
20.
E. Träbert H.-P. Garnir P.-D. Dumont T. Bastin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):25-31
Peculiar properties of ion-atom collision systems, in particular deviations from statistical populations of singlet and triplet
levels, can be studied by optical spectroscopy. We have extended earlier studies by VUV spectroscopy of a number of collision
systems at various collision energies in the 0.01-MeV/nucleon to 1-MeV/nucleon range, involving H2
+, H+, He+, He2+, Ne+, Ar+, and N2
+ as projectiles and Ne, Ar, and N2 as target gases. Statistically significant deviations of the relative intensities of singlet and triplet lines from simple
ratios are observed in the displaced terms of the valence shell of Ne III, corroborating and extending earlier work. For Ar
III, the energy dependences of singlet-to-triplet excitation ratios are very different for different projectiles. For N II,
in contrast, all observed line ratios are practically independent of the projectile energy.
Received 17 November 2000 and Received in final form 31 January 2001 相似文献