共查询到20条相似文献,搜索用时 31 毫秒
1.
F. Rebentrost S. Klose J. Grosser 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):277-289
We apply quantum and semiclassical theories to differential optical collisions Na(32S1/2) + Kr +
Na(32P1/2,3/2) + Kr. Our results provide a basis to analyze recent experiments in which for the first time optical collisions were investigated
with angular resolution under crossed-beam conditions. A characteristic feature of the differential cross sections is the
pronounced oscillatory structure due to interferences of different Condon paths. These Stueckelberg oscillations form an extremely
sensitive probe of the collisional dynamics and of the molecular interactions. We demonstrate perspectives to determine geometric
properties of the collision complex by excitation with polarized light. By final state analysis nonadiabatic (spin-orbit,
rotational) interactions can be studied with complete control of the path. In summary it is shown that the method of differential
detection of optical collisions opens a variety of new accesses to atomic and molecular subcollisions.
Received: 30 July 1997 / Received in final form: 5 November 1997 / Accepted: 8 January 1998 相似文献
2.
G. Guillon T. Stoecklin A. Voronin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):83-87
We compare the cross sections for the transitions changing the projection of
the total angular momentum of N2
+(2Σ) in collisions
with 3He and 4He at very low collision energy. The fundamental
states of the two nuclear spin isomers of N2
+ are considered as
well as the two fine structure levels of the first excited para level N=2.
It is shown that the two fundamental states of the two nuclear spin isomers
behave differently. For the fundamental para level N=0 of N2
+, the
projection changing cross section is always negligible compared to the
elastic one for both He isotopes. For the fundamental ortho level N=1 of
N2
+, the spin-rotation interaction couples the different spin
levels directly so the spin relaxation becomes a first order process. The
associated resonances increase the projection changing cross section which
remains smaller but becomes comparable with the elastic one. This is in
contrast with the excited rotational levels of N2
+, which for the
rotational deactivation and elastic channels are found to be equal around
the resonances for the collisions involving 3He. These two channels are
always larger than the projection changing one. We also find that, for
transitions involving the fundamental rotational state, the domain of
validity of the threshold laws discussed by Krems and Dalgarno [Phys. Rev. A 67, 050704 (2003)] for a potential decreasing faster than
1/r2 is shortened, due to the long range charge induced dipole potential.
This effect is illustrated for the collisions of 3He with the
fundamental para state of N2
+. 相似文献
3.
T. Stoecklin A. Voronin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):259-265
A quantum mechanical investigation of vibrational and rotational energy transfer in cold and ultra cold collisions of CH+ with 3He and 4He atoms is presented. Ab initio potential energy calculations are carried out at the BCCD(T) level and a global 3D potential
energy surface is obtained using the Reproducing Kernel Hilbert Space (RKHS) method. Close coupling scattering calculations
using this surface are performed at collision energy ranging from 10-6 to 2000 cm-1. In the very low collision energy
limit, the vibrational and rotational quenching cross sections of CH+ in collisions with He are found to be of the same order of magnitude. This unusual result is attributed to the large angular
anisotropy of the intermolecular potential and to the unusually small equilibrium value of the Jacobi R coordinate of the
He–CH+ complex. As for the He–N2
+ collision, we also find a strong isotope effect in the very low collision energy range which is analyzed in terms of scattering
length and the differences between these two collisions are also discussed. 相似文献
4.
C. Vadla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):259-264
The total rate coefficient k for the energy pooling process has been measured in dependence on the ratio of the number densities of the Cs 6P fine-structure sublevels. The measurements
were performed applying the laser fluorescence method. From the set of the obtained data for k, the rate coefficients for the particular collisions were derived. The obtained values for the and collisions at T
= 600 K are , and , respectively. The value for k1 and the estimate for k3 are consistent with the data previously published by other authors. The rate coefficient k2 is reported for the first time.
Received: 10 June 1997 / Revised: 13 October 1997 / Accepted: 5 January 1998 相似文献
5.
A. Fioretti E. Arimondo A. Crubellier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):219-225
The measurements of fine-structure changing collisions in a cesium magneto-optical trap, reported in a previous work [A. Fioretti
et al., Phys. Rev. A 55, R3999 (1997)], are reanalyzed within a model based on the flux enhancement effect, which takes place in cold atomic collisions.
In the present analysis, we consider the cooperative effect of the long-range and the shorter-range excitation by the strong
trap laser. We evidence also the important role of the hyperfine structure of the Cs2 molecular levels asymptotically connected to the ground-state and excited-state dissociation limits.
Received 22 July 1999 and Received in final form 4 May 2000 相似文献
6.
B. H. Yang P. C. Stancil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):351-358
Quantum close-coupling and coupled-states approximation
scattering calculations for rotational energy transfer
of rotationally excited NH3 and ND3 due to collisions with He
are presented. Calculations were performed for collision
energies between 10-5 and 10 000 cm-1
using the NH3-He potential of Hodges and Wheatley [J. Chem. Phys.
114, 8836 (2001)]. State-to-state and total quenching cross sections from
some selected initial states are presented.
Rate coefficients for ortho-NH3 for the quenching 10+→00+
transition were obtained on potentials scaled to reproduce measurements
of second virial coefficients with the results showing strong sensitivity
to the potential, especially at low temperatures. Significant isotope
effects are found in quenching cross sections in the cold to ultracold
regime particularly in the region dominated by quasi-bound resonances,
~0.1 to 10 cm-1. As ammonia has been translationally cooled
via Stark deceleration methods, it is a good candidate for experimental
study of such effects at cold temperatures.
Comparison of rate coefficients with available theoretical results
are also presented. 相似文献
7.
G. Guillon T. Stoecklin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):359-371
A comparative study of the inelastic
scattering
of 14N2
+ and
14N2 in collision with 3He atoms is presented. The
unrestricted nearside-farside (NF) method proposed by
Connor [J. Chem. Phys. 104, 2297 (1995)] is applied to analyse the Close
Coupling rotationally state selected angular distributions for four kinetic
energies. These four energies illustrate different regimes of the dynamics.
The relationships between the structures of the calculated differential
cross-sections (DCS) and the different regions of the potential energy
surfaces involved which can be extracted from semi classical models are here
easily obtained from a simple reading of the (NF) figures. At the
higher energy far-off the wells (1000 cm-1) the shape of the DCS are
quite similar for the two systems and their nearside-farside components
also, showing that the inelastic process is controlled by the short range
repulsive part of the potential which is essentially the same for these two
collisions. When the energy is decreased the differences between the two
wells associated with the He–N2
+ and He–N2 complexes are
responsible for the differences between the DCS for the two systems. The
farside component associated with the well become more and more prominent
for the elastic scattering while inelastic scattering remains controlled by
the repulsive core in a large angular interval. The nearside farside
analysis gives also a new picture of a resonance which is regarded as an
equilibrium between the repulsive and the attractive parts of the potential. 相似文献
8.
P. Sigmund A. Schinner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):425-434
The Bohr theory treats charged-particle stopping as a sequence of interactions with classical target electrons bound harmonically
to their equilibrium positions. We demonstrate that equivalent results can be derived on the assumption of free binary collisions
governed by a suitable effective potential. This kind of mapping is rigorous in the limits of distant and close collisions
and therefore provides a tool to evaluate energy losses via binary-scattering theory. This model was developed with the aim of calculating stopping forces for heavy ions at moderately
high velocities, where a classical-orbital calculation is typically superior to the Born approximation. The effective potential
employed holds equally well for dressed as for stripped ions. Unlike the Bohr theory, the present evaluation avoids a formal
division into regimes of close and distant collisions that do not necessarily join smoothly. Moreover, no perturbation expansion
is necessary. For these reasons the overall accuracy as well as the range of validity of the Bohr model are significantly
enhanced. Extensive tests have been performed, including comparisons with rigorous evaluations of the Z
1
3 effect, with excellent agreement even where such was not necessarily expected. Moreover, credible results have been obtained
under conditions where the perturbation expansion shows poor convergence. A comparison with experimental data on O–Al is encouraging,
even though shell corrections and projectile excitation/ionization have not yet been incorporated and input has not yet been
optimized.
Received 21 April 2000 and Received in final form 16 June 2000
An erratum to this article is available at . 相似文献
9.
R.A. Sultanov W. Sandhas V.B. Belyaev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(1):33-37
Muon-transfer rates in collisions of hydrogen-like atoms or with light nuclei t, 3He, 4He, 6Li or 7Li, are calculated in a semiclassical approximation to the Faddeev-Hahn equations. The two nuclei involved are treated classically,
while the motion of the muon in their Coulomb field is considered from the quantum mechanical point of view. The experimentally
observed strong dependence on the charge of the nuclei is reproduced.
Received: 1st November 1997 / Revised: 26 March 1998 / Accepted: 18 August 1998 相似文献
10.
S. Martin J. Bernard L. Chen A. Denis J. Désesquelles 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):1-6
Electron capture by Ar8+ in collisions with C60 fullerene has been investigated using coincident measurements of the number n of ejected electrons, the mass and charge of multicharged Cr+
60
recoil ions and their fragments Ci+
m and the final charge state of outgoing projectiles Ar(8-s)+ (). The number of captured electrons r is the sum of the numbers of stabilized and emitted electrons: r
=
n
+
s. The ratio n
/
s decreases by a factor three with s increasing from 1 to 7 showing that the multiply excited states populated by capture of a large number of electrons are rather
stable against auto-ionisation. Each kinetic energy spectrum of Ar+ and Ar2+ projectiles is composed of two peaks which we attribute to collisions “inside” and “outside” the C60 cage. The measured energy shift of the projectile keV is consistent with the corresponding energy loss keV in a carbon foil with an equivalent thickness. Inside collisions are characterized by a strong dissociation of recoil
ions into light monocharged fragments and by a high multiplicity of ejected electrons.
Received: 25 March 1998 / Received in final form and Accepted: 9 June 1998 相似文献
11.
A.T. Hartlieb D. Markus W. Kreutner K. Kohse-Höinghaus 《Applied physics. B, Lasers and optics》1997,65(1):81-91
2 Σ+) was measured in a low-pressure H2/O2 flame for three rotational levels of OH (v′=1). Rate coefficients for collisions with H2O and N2 were determined. At 1600 K, kVET (N2) is (in 10-11 cm3s-1) 10.1±2, 6.1±1.8, and 3.8±1.3 for N′=0, 5, and 13, respectively. The kVET (H2O) is <1.1±1.8. The kQ (N2) is <2.4±8 for both vibrational levels. The kQ (H2O) in v′=1 is 59.1±6.5, 54.7±6.4, and 54.9±6.6 for N′=0, 5, and 13, respectively, and, determined indirectly, 74.6±10.4, 70.6±10.3, and 63.4±7.3 for N′=0, 5, and 13 in v′=0. A multi-level model of OH population dynamics, which is being developed for the quantitative simulation of experimental
LIF spectra, was extended to include VET. It was attempted to simulate state-to-state-specific VET coefficients for N2 collisions. From these simulations it appears that angular momentum conservation does not determine the N dependence of the
vibrational relaxation step.
Received: 9 September 1996/Revised version: 6 January 1997 相似文献
12.
We investigate the production of long-lived metastable (43
P
2
) calcium atoms in a magneto-optical trap (MOT) operating on the 41
S
0
?41
P
1
transition at 423 nm. For excited 41
P
1
atoms a weak decay channel into the triplet states 43
P
2
and 43
P
1
exists via the 31
D
2
state. The undesired 43
P
1
atoms decay back to the ground state within 0.4 ms and can be fully recaptured if the illuminated trap volume is sufficientlylarge.
We obtain a flux of above 1010 atoms/s into the 43
P
2
state. We find that our MOT lifetime of 23 ms is mainly limited by this loss channel, and thus the 43
P
2
production is not hampered by inelastic collisions. If we close the loss channel by repumping the 31
D
2
atoms with a 671 nm laser back into the MOT cycling transition, a non-exponential 72 ms trap decay is observed, indicating
the presence of inelastic two-body collisions between 41
S
0
and 41
P
1
atoms.
Received: 10 July 2001 / Revised version: 22 October 2001 / Published online: 23 November 2001 相似文献
13.
L.G. Marcassa R.A.S. Zanon S. Dutta J. Weiner O. Dulieu V.S. Bagnato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):317-321
Using a technique that consists in ionizing atoms out of the 5P
1/2
fragments originated in the cold collision process, we have measured the contribution of the fine structure changing collision
(FS) to the total trap loss rate of cold 85Rb. Our results show that FS contribution is responsible for about 4% of the total trap loss. This result should stimulate
new theoretical discussions involving exoergic cold collisions.
Received 26 October 1998 and Received in final form 2 February 1999 相似文献
14.
We report the first experimental observation of the excitation of the 4p
2
P
3/2, 1/2 resonance states of Ca II (located at 74 720.4 and 74 497.5 cm–1 above the ground state of Ca I) following pulsed-laser pumping of the 4s
2
1
S
O–4s4p
3P1 intercombination transition of Ca I (E
ex = 15 210 cm–1). Large scale collisional transfer of energy between the laser-excited atoms is believed to be responsible for this. This is possibly because sufficient time is available (rad of the 4s4p
3
P
1 state is approximately 350 µs) for collisions to build such a high level of excitation. Some interesting additional features of the fluorescence spectra of the laser-pumped Ca vapor, such as temperature dependence of the fluorescence intensities and evolution in time of some selected states, are also presented. 相似文献
15.
E.A. Alipieva S.I. Karabasheva 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):291-294
The non-linear Voigt effect has been studied in He discharge under resonance laser interaction with the He transition. The range of non-linear signal existence was determined. The contribution of the lower and upper states to
the overall signal was analyzed. The cross-section for depolarizing collisions with ground state He atoms was estimated for
the 33
D
2,3
He state.
Received: 16 June 1998 / Received in final form: 14 December 1998 相似文献
16.
V. M. Bystritsky V. V. Gerasimov J. Woźniak 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):79-84
The measurement method and results measuring of the stopping
power ratio of helium-3 and deuterium atoms for muons slowed down
in the D/3He mixture are presented. Measurements were performed
at four values of pure 3He gas target densities, ϕHe
= 0.0337, 0.0355, 0.0359, 0.0363 (normalized to the liquid
hydrogen density) and at a density 0.0585 of the D/3He mixture.
The experiment was carried out at PSI muon beam μE4 with the
momentum Pμ= 34.0 MeV/c. The measured value of the mean
stopping ratio S$_{3^He/D}$ is 1.66±0.04. 相似文献
17.
S. Tomita J.S. Forster P. Hvelplund A.S. Jensen S.B. Nielsen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):119-122
We have measured attenuation cross sections and fragmentation cross sections for protonated water clusters H(H2O)n
+ (n = 1 to 100) colliding with noble gas atoms (He and Xe) at a laboratory energy of 50 keV. In collisions with He, a transparency
effect in the attenuation cross section was observed. For the case of fragmentation in collisions with Xe, a strong enhancement
of small clusters was observed which we attribute to multifragmentation.
Received 30 November 2000 相似文献
18.
B. H. Yanga P. C. Stancil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(3):317-324
Quantum close-coupling and coupled-state approximation scattering calculations for rotational energy transfer of rotationally
excited CH4 due to collisions with He are presented for collision energies between 10−7 and 3000 cm−1 using the MP4 potential of Calderoni et al. [J. Chem. Phys. 121, 8261 (2004)]. State-to-state cross sections and rate coefficients
from selected initial rotational states of CH4 in symmetries A, E, and F are studied from the ultra-cold to the thermal regime. Comparison of the cross sections with available theoretical results
and experimental data show good agreement. Applications to astrophysics and cold laboratory environments are briefly addressed. 相似文献
19.
M.L. Gardel R. Vandenbosch B.P. Henry C. Cooper D.I. Will 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):79-81
The destruction cross-section for 22.5 and 50 keV C1- , for 10 and 50 keV C8
1- and for 50 and 75 keV C60
1- clusters in collisions with H2 has been measured by an attenuation method. The destruction of the cluster anions is dominated by electron detachment rather
than fragmentation and is of the order of the geometric cross-section. The cross-sections vary little with bombarding energy.
Received: 16 September 1998 / Received in final form: 23 February 1999 相似文献
20.
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