共查询到19条相似文献,搜索用时 62 毫秒
1.
利用激光蒸发团簇源产生Wn团簇束,团簇束通过一个充有N2气体分 子的低压反应池,利用飞行时间质谱探测反应产物,在类单次碰撞条件下研究了W+10 -W+50和N2分子的反应性,在室温条件下测量了N2分子与W+n团簇反应的 反应几率。团簇尺寸在10~26原子的团簇与N2分子的反应几率与团簇尺寸有很强的相关性 ,对n=16,22,23的团簇具有比较高的反应性。W+n与N2分子的反应性与Wn与N 2分子的反应性显示出相似的规律性。 相似文献
2.
用激光蒸发团簇源产生Wn团簇束 ,团簇通过一个充有N2 气体分子的低压反应池 ,利用飞行时间质谱探测反应产物 ,在单次碰撞条件下研究了W+ 10 —W+ 50 和N2 分子的反应性 ,在室温条件下测量了N2 分子与W+ n 团簇反应的反应几率 .n =10— 2 6的团簇与N2 分子的反应几率与团簇尺寸有很强的相关性 ,n =16 ,2 2 ,2 3的团簇有较高的反应性 .W+ n 与N2 分子的反应性与Wn与N2 分子的反应性显示出相似的规律性. A beam of tungsten clusters, seeded in He gas, is produced in a pulsed laser vaporization source. We have studied the size-dependent reactivity of positive tungsten cluster ions with N 2 under single-collision conditions by using laser-vaporization source, low-pressure reaction cell and time-of-flight mass spectrometer. The reaction probability with N 2 molecule was measured as a function of cluster size, W + 10-W + 50, for clusters produced at room temperature... 相似文献
3.
介绍了同步辐射、特别是第三代同步辐射对原子、分子和团簇物物理研究的意义。第三代同步辐射光源能力它们提供哪些新的实验手段是上述邻内广大研究人员共同关心的问题,作者尝试表明自己的一些观点。 相似文献
4.
采用紧密结合分子动力学模型,对Na9+Na9碰撞系统在质心系中单原子的轰击能量为Ecm/n=0.0063eV的对心碰撞进行了研究。从动力学的观战对双团簇分子(Na9)2的形成给预了证明,结合所谓“「突然冷却”技术,鉴别出所形成的(Na9)2,并给出了其结构性质。 相似文献
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报道了关于H+4团簇的实验研究结果,从H+4的分解能谱发现可能存在H3团簇.分析讨论了H+4的形成方式和可能的分解途径. 相似文献
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10.
报道了H+5的实验结果.分析讨论了H+5的形成和分解途径.根据理论分析,以稳定的H+3为核心与一个或多个氢分子结合可能形成稳定的H+n氢团簇离子.另一方面,在高频离子源中, 有发生H+3与H2反应的条件.实验中,从高频离子源引出的离子束被静电加速器加速,然后用90°磁分析器选择质量数为5的离子,再将这些离子偏转20°,最后在20°方向测量它们的能谱.从能谱发现,在高频离子源中可能通过H+3与H2的离子-分子反应形成了H+5团簇离子;并且在H+5的分解产物中还发现可能存在H3和H4等中性团簇产物. 相似文献
11.
L. Schweikhard K. Hansen A. Herlert G. Marx M. Vogel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):137-143
Ion traps are wall-less containers which allow the
extended storage of selected species. During the storage various
interaction steps may be repeatedly applied. To this end no
further hardware has to be added - in contrast to beam
experiments. In this progress report two examples of recent
developments are presented: the experiments have been performed
with metal clusters stored in a Penning (ion cyclotron
resonance) trap. A new experimental scheme has been developed
which allows precision measurements of the dissociation energies
of polyatomic species. It has been triggered by investigations
on the delayed photodissociation of stored metal clusters.
However, the technique is also readily available for application
to a broad variety of different species and it is not even
restricted to trapping experiments. The second development is
more closely connected with ion storage in Penning traps: by
application of an electron bath singly charged anionic
clusters can be converted into multiply charged species.
Subsequently, they are charge selected and investigated with
respect to their reaction upon excitation. In particular,
preliminary results indicate that dianionic metal clusters emit
two electrons upon photoexcitation whereas the singly charged
species show dissociation. 相似文献
12.
K. Guch J. Fedor S. Matt-Leubner R. Parajuli C. Mair A. Stamatovic O. Echt C. Lifshitz J. Harvey F. Hagelberg Z. Herman M. Probst P. Scheier T. D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):131-136
The recent addition of (i) a third sector field to our two
sector field mass spectrometer (resulting in a BE1E2 field
configuration) and of (ii) a high performance electron gun
enables us now to study in detail the time dependence of the
kinetic energy release distribution (KERD) over a relatively
wide range of cluster ion lifetimes. Using this newly
constructed device we have studied here for the first time KERDs
and deduced binding energies BEs (using finite heat bath theory)
of large rare gas cluster ions (an upper size limit in earlier
studies arose from the fact that different naturally occurring
isotopes will contribute to a chosen metastable peak when the
size exceeds a certain value) and in addition of fullerene ions
smaller and larger than
(here again contaminating
coincidences did not allow such studies earlier). Moreover, high
precision KERD measurements for the decay of rare gas dimer ions
in conjunction with model calculations (using recently
calculated potential energy curves for the rare gas dimer ions)
also enable us to obtain information on the dynamics and the
mechanisms of the underlying spontaneous decay reactions
. In addition, we are also reporting
here a novel method (unified breakdown graph method) to
determine cluster ion binding energies using a recently
constructed tandem mass spectrometer BESTOF allowing us to
measure fragmentation patterns arising from the unimolecular
decay of molecular cluster ions induced by surface collisions.
The fragmentation and reaction patterns of protonated ethanol
cluster ions investigated here clearly demonstrate in contrast
to some of the earlier cluster ion studies that unimolecular
dissociation kinetics determines the formation of product ions
in the surface-induced decomposition. 相似文献
13.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier I. Tignères 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):185-192
The cross-sections for collisional charge transfer between singly charged free clusters M
n
+ (M = Li, Na; n=1...50) and atomic targets A (cesium, potassium) have been measured as a function of collisional relative velocity in laboratory
energy range 1–10 keV. For each cluster size, the experimental values of the charge transfer cross-section are fitted with an universal parametric curve with two independent parameters and vm, the maximum cross-section and the corresponding velocity. For small size clusters (), the characteristic parameters show strong variations with the number of atoms in the cluster. Abrupt dips observed for n=10 and n=22 are attributed to electronic properties. Charge transfer patterns observed for various collisional systems present similarities,
which appear more sensitive to cluster quantum size effects than to collision energy defects. In their whole, the and vm parameters show differences in both their size evolution and their absolute values discussed in term of projectile and target
electronic structures.
Received 13 April 2000 and Received in final form 29 June 2000 相似文献
14.
J.M. Mestdagh M. Berdah N. Auby C. Dedonder-Lardeux C. Jouvet S. Martrenchard-Barra D. Solgadi J.P. Visticot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):291-302
The photodissociation of a chlorine molecule in the environment of a xenon cluster has been studied experimentally using the
real time pump and probe technique through the formation of an XeCl reaction product. The photodissociating system is probed
in such a way that the movement of a single chlorine atom in the xenon environment is detected. Various XenCl2 cluster sizes have been investigated leading to the distinction between uncapped, half-capped and doubly capped structures
for these clusters. These structures have a profound influence on the photodissociation dynamics. Retrapping of one chlorine
atomic fragment and stabilization of the XeCl reaction product is only observed for the half and doubly capped clusters. The
experimental work is complemented by classical molecular dynamics calculations to get a full picture of the photodissociation.
Received: 17 February 1998 / Received in final form and Accepted: 28 July 1998 相似文献
15.
Summary We study the fragmentation of the dipole collective states in silver cluster ions by looking at the coupling with surface
oscillations and deformations of a dropletlike structure. This coupling is found to be crucial in order to reproduce the experimental
photoabsorption data in open-shell clusters. 相似文献
16.
Total electron yields for perpendicular impact of C+ ions on W have been measured for projectile energies from 0.2 keV to 7 keV. The data are compared with the data of C+ bombardment of gold and graphite in order to demonstrate general trends in kinetic electron yields at low projectile velocities. The total electron yields in the studied combinations of projectiles and substrates show a similar exponential dependence Γ ∝ (v/A) exp(−A/v), where A is a constant and v is the projectile velocity. 相似文献
17.
N. Hori A. Furuya M. Tsuruta F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):41-44
Photoinduced dissociation in the ultraviolet region has been investigated for Ag nF n-1
+ cluster ions. Photodissociation spectrum of
Ag2F+
in the energy of 3.8–5.6 eV exhibits several sharp bands corresponding to the transition to electronically excited states.
In this dissociation, only the Ag2
+ ion was observed as a fragment ion. Theoretical calculation indicates that the parent Ag2F+ ion has a linear Ag-F-Ag equilibrium geometries in the ground and excited states. Since conformational changes by excitation
of bending vibration are necessary for the fragmentation of an F atom, this indicates that production of Ag2
+ from Ag2F+ is a result of internal conversion and following conformational changes. 相似文献
18.
Wengang Zheng 《Surface science》2006,600(10):2207-2213
H2 dissociation on polycrystalline tungsten is measured from 1700 to 3000 K using the filament temperature (T) change and a normalized H-atom density at the chamber surface. The dissociation probability per H2 filament collision (Pdiss) saturates at 0.40 at high T and has a 2.25 ± 0.05 eV apparent activation energy when Pdiss ? 1. This activation energy is consistent with prior data and models, but the H2 pressure dependence is not. Pdiss is independent of the H2 pressure for this entire T range and the 1-85 mTorr pressure range studied, contradicting the primary model that has been used to explain H2 dissociation on tungsten and other metals. We show that some apparently contradictory prior measurements are actually consistent with our observations and with each other, once this pressure dependence of Pdiss is recognized. 相似文献
19.
SiC is a highly stable material in bulk. On the other hand, alloys of silicon and carbon at nanoscale length are interesting from both technological as well fundamental view point and are being currently synthesized by various experimental groups (Truong et. al., 2015 [26]). In the present work, we identify a well-known silicon cluster viz., Si10 and dope it sequentially with carbon atoms. The evolution of electronic structure (spin state and the structural properties) on doping, the charge redistribution and structural properties are analyzed. It is interesting to note that the ground state SiC clusters prefer to be in the lowest spin state. Further, it is seen that carbon atoms are the electron rich centres while silicon atoms are electron deficient in every SiC alloy cluster. The carbon–carbon bond lengths in alloy clusters are equivalent to those seen in fullerene molecules. Interestingly, the carbon atoms tend to aggregate together with silicon atoms surrounding them by donating the charge. As a consequence, very few Si–Si bonds are noted with increasing concentrations of C atoms in a SiC alloy. Physical and chemical stability of doped clusters is studied by carrying out finite temperature behaviour and adsorbing O2 molecule on Si9C and Si8C2 clusters, respectively. 相似文献