scholarly journals Long-range versus short-range effects in cold molecular ion-neutral collisions

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Alexander D. Dörfler ◽  
Pascal Eberle ◽  
Debasish Koner ◽  
Michał Tomza ◽  
Markus Meuwly ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Theoretical Analysis ◽  
Ab Initio ◽  
Long Range ◽  
Short Range ◽  
Experimental Results ◽  
Quantum Scattering ◽  
Kinetics And Dynamics ◽  
Reaction Channels ◽  
Ab Initio Potentials

AbstractThe investigation of cold interactions between ions and neutrals has recently emerged as a new scientific frontier at the interface of physics and chemistry. Here, we report a study of charge-transfer (CT) collisions of Rb atoms with N$${}_{2}^{+}$$2+ and O$${}_{2}^{+}$$2+ ions in the mK regime using a dynamic ion-neutral hybrid trapping experiment. We observe markedly different CT kinetics and dynamics for the different systems and reaction channels studied. While the kinetics in some channels are consistent with classical capture theory, others show distinct non-universal dynamics. The experimental results are interpreted with the help of classical-capture, quasiclassical-trajectory and quantum-scattering calculations using ab-initio potentials for the highly excited molecular states involved. The theoretical analysis reveals an intricate interplay between short- and long-range effects in the different reaction channels which ultimately determines the CT dynamics and rates. Our results illustrate salient mechanisms that determine the efficiency of cold molecular CT reactions.

Modulation of Surface Charge Transfer through Competing Long-Range Repulsive versus Short-Range Attractive Interactions

2011 ◽  
Vol 115 (38) ◽  
pp. 18640-18648 ◽  
Author(s):  
J. Fraxedas ◽  
S. García-Gil ◽  
S. Monturet ◽  
N. Lorente ◽  
I. Fernández-Torrente ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Surface Charge ◽  
Long Range ◽  
Short Range

scholarly journals 1st Row Transition Metal Aluminylene Complexes: Preparation, Properties and Bonding Analysis

2021 ◽  
Author(s):  
Richard Y Kong ◽  
Mark Crimmin
Keyword(s):  
Transition Metal ◽  
Ab Initio ◽  
Long Range ◽  
Short Range ◽  
Dispersion Interactions ◽  
Metal Centre ◽  
Bonding Analysis ◽  
Metal Metal ◽  
Spectroscopic Characterisation ◽  
Insight Into

<i>The synthesis and spectroscopic characterisation of eight new first-row transition metal (M = Cr, Mn, Fe, Co, Cu) aluminylene complexes is reported. DFT and ab<b> </b>initio calculations have been used to provide detailed insight into the metal–metal bond. The σ-donation and π-backdonation properties of the aluminylene ligand are evaluated via NBO and ETS-NOCV calculations. These calculations reveal that these ligands are strong σ-donors but also competent π-acceptors. These properties are not fixed but vary in response to the nature of the transition metal centre, suggesting that aluminylene fragments can modulate their bonding to accommodate both electron-rich and electron-poor transition metals. Ab initio<b> </b>DLPNO-CCSD(T) calculations show that dispersion plays an important role in stabilising these complexes. Both short-range and long-range dispersion interactions are identified. These results will likely inform the design of next-generation catalysts based on aluminium metalloligands. </i>

scholarly journals 1st Row Transition Metal Aluminylene Complexes: Preparation, Properties and Bonding Analysis

2021 ◽  
Author(s):  
Richard Y Kong ◽  
Mark Crimmin
Keyword(s):  
Transition Metal ◽  
Ab Initio ◽  
Long Range ◽  
Short Range ◽  
Dispersion Interactions ◽  
Metal Centre ◽  
Bonding Analysis ◽  
Metal Metal ◽  
Spectroscopic Characterisation ◽  
Insight Into

<i>The synthesis and spectroscopic characterisation of eight new first-row transition metal (M = Cr, Mn, Fe, Co, Cu) aluminylene complexes is reported. DFT and ab<b> </b>initio calculations have been used to provide detailed insight into the metal–metal bond. The σ-donation and π-backdonation properties of the aluminylene ligand are evaluated via NBO and ETS-NOCV calculations. These calculations reveal that these ligands are strong σ-donors but also competent π-acceptors. These properties are not fixed but vary in response to the nature of the transition metal centre, suggesting that aluminylene fragments can modulate their bonding to accommodate both electron-rich and electron-poor transition metals. Ab initio<b> </b>DLPNO-CCSD(T) calculations show that dispersion plays an important role in stabilising these complexes. Both short-range and long-range dispersion interactions are identified. These results will likely inform the design of next-generation catalysts based on aluminium metalloligands. </i>

A General Approach for Word Reordering in English-Vietnamese-English Statistical Machine Translation

2015 ◽  
Vol 24 (06) ◽  
pp. 1550024
Author(s):  
Nhung T. H. Nguyen ◽  
Vinh Q. Le ◽  
Minh-Quoc Nghiem ◽  
Dien Dinh
Keyword(s):  
Machine Translation ◽  
Long Range ◽  
Word Order ◽  
Short Range ◽  
Statistical Machine Translation ◽  
Experimental Results ◽  
Translation Quality ◽  
Part Of Speech

Word ordering is among the most important problems in machine translation. In this paper, we describe a general approach to solve this problem in English-Vietnamese- English statistical machine translation. Our model automatically extracts short-range and long-range reordering rules based on part-of-speech tags and alignment information. Our method, therefore, covers both local and global word order, and is more versatile than other methods. To obtain a better set of reordering rules, we omit generated rules if their weight is lower than a threshold [Formula: see text]. The experimental results have shown that the translation quality has been improved significantly compared to the distance-based reordering model and comparable to the lexicalized model. Our approach is not only suitable for English-Vietnamese but also for language pairs which have many differences in syntax, such as English-Chinese and Chinese-Vietnamese.

scholarly journals RANGE-DEPENDENT DISORDER EFFECTS ON THE PLATEAU-WIDTHS CALCULATED WITHIN THE SCREENING THEORY OF THE IQHE

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1362-1371 ◽  
Author(s):  
AFIF SIDDIKI ◽  
ROLF R. GERHARDTS
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Long Range ◽  
Potential Distribution ◽  
Short Range ◽  
Filling Factor ◽  
Quantum Hall ◽  
Experimental Results ◽  
Potential Fluctuations ◽  
Disorder Effects

We summarize the screening theory of the integer quantized Hall effect (IQHE) and emphasize its two key mechanisms: first, the existence, in certain magnetic field intervals, of incompressible strips, with integer values of the local filling factor and quantized values of longitudinal and Hall resistivity, and second, the confinement of an imposed dissipative current to these strips, leading to the quantization of the global resistances. We demonstrate that, without any localization assumption, this theory explains the enormous experimental reproducibility of the quantized resistance values, as well as experimental results on the potential distribution in narrow Hall bars. We further demonstrate that inclusion of long-range potential fluctuations allows to apply the theory to wider Hall bars, and can lead to a broadening of the quantum Hall plateaus, whereas short-range disorder tends to narrow the plateaus.

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