Electron-induced molecular dissociation at a surface leads to reactive collisions at selected impact parameters

2019 ◽  
Vol 214 ◽  
pp. 89-103 ◽  
Author(s):  
Kelvin Anggara ◽  
Lydie Leung ◽  
Matthew J. Timm ◽  
Zhixin Hu ◽  
John C. Polanyi
Keyword(s):  
Impact Parameter ◽  
Reaction Dynamics ◽  
Molecular Dissociation ◽  
Reactive Collisions ◽  
Impact Parameters ◽  
The Impact ◽  
Collimated Beam

A collimated beam of ‘projectiles’ strikes a chemisorbed ‘target’ thereby selecting the impact parameter, achieving an elusive goal of reaction dynamics.

scholarly journals Approaching the forbidden fruit of reaction dynamics: Aiming reagent at selected impact parameters

2018 ◽  
Vol 4 (10) ◽  
pp. eaau2821 ◽  
Author(s):  
Kelvin Anggara ◽  
Lydie Leung ◽  
Matthew J. Timm ◽  
Zhixin Hu ◽  
John C. Polanyi
Keyword(s):  
Impact Parameter ◽  
Reaction Dynamics ◽  
Bimolecular Reaction ◽  
Important Variable ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Stationary Target ◽  
Impact Parameters ◽  
Miss Distance ◽  
The Impact

Collision geometry is central to reaction dynamics. An important variable in collision geometry is the miss-distance between molecules, known as the “impact parameter.” This is averaged in gas-phase molecular beam studies. By aligning molecules on a surface prior to electron-induced dissociation, we select impact parameters in subsequent inelastic collisions. Surface-collimated “projectile” molecules, difluorocarbene (CF2), were aimed at stationary “target” molecules characterized by scanning tunneling microscopy (STM), with the observed scattering interpreted by computational molecular dynamics. Selection of impact parameters showed that head-on collisions favored bimolecular reaction, whereas glancing collisions led only to momentum transfer. These collimated projectiles could be aimed at the wide variety of adsorbed targets identifiable by STM, with the selected impact parameter assisting in the identification of the collision geometry required for reaction.

scholarly journals A note on the relations between elastic and inelastic interactions and increasing ratio σel(s)/σtot(s) at the LHC

2019 ◽  
Vol 34 (32) ◽  
pp. 1950259 ◽  
Author(s):  
S. M. Troshin ◽  
N. E. Tyurin
Keyword(s):  
Elastic Scattering ◽  
Energy Dependence ◽  
Impact Parameter ◽  
Cross Sections ◽  
Parameter Dependence ◽  
Slope Parameter ◽  
Short Notice ◽  
Inelastic Interactions ◽  
The Impact ◽  
Mode A

We comment briefly on relations between the elastic and inelastic cross-sections valid for the shadow and reflective modes of the elastic scattering. Those are based on the unitarity arguments. It is shown that the redistribution of the probabilities of the elastic and inelastic interactions (the form of the inelastic overlap function becomes peripheral) under the reflective scattering mode can lead to increasing ratio of [Formula: see text] at the LHC energies. In the shadow scattering mode, the mechanism of this increase is a different one, since the impact parameter dependence of the inelastic interactions probability is central in this mode. A short notice is also given on the slope parameter and the leading contributions to its energy dependence in both modes.

SOME CHARACTERISTICS OF THE COMPOUND MULTIPLICITY IN HIGH-ENERGY NUCLEUS–NUCLEUS INTERACTIONS

2011 ◽  
Vol 20 (08) ◽  
pp. 1735-1754 ◽  
Author(s):  
M. MOHERY ◽  
M. ARAFA
Keyword(s):  
Experimental Data ◽  
Impact Parameter ◽  
Mass Number ◽  
Multiplicity Distribution ◽  
High Energy ◽  
Projectile Nucleus ◽  
Target Mass ◽  
Compound Multiplicity ◽  
Multiplicity Distributions ◽  
The Impact

The present paper deals with the interactions of 22 Ne and 28 Si nuclei at (4.1–4.5)A GeV /c with emulsion. Some characteristics of the compound multiplicity nc given by the sum of the number of shower particles ns and grey particles ng have been investigated. The present experimental data are compared with the corresponding ones calculated according to modified cascade evaporation model (MCEM). The results reveal that the compound multiplicity distributions for these two reactions are consistent with the corresponding ones of MCEM data. It can also be seen that the peak of these distributions shifts towards a higher value of nc with increasing projectile mass. It may further be seen that the compound multiplicity distributions becomes broader with increasing target size and its width increases with the size of the projectile nucleus. In addition, it has been found that the MCEM can describe the compound multiplicity characteristics of the different projectile, target and the correlation between different emitted particles. The values of average compound multiplicity increase with increasing mass of the projectile. Furthermore, it is observed that while the value of 〈nc〉 depends on the mass number of the projectile Ap and the target mass number At, the value of the ratio 〈nc〉/D(nc) seems to be independent of Ap and At. The impact parameter is found to affect the shape of the compound multiplicity distribution. Finally, the dependence of the average compound multiplicity on the numbers of grey and black particles, and the sum of them, is obvious. The values of the slope have been found to be independent of the projectile nucleus.

THE CDF LAYER 00 DETECTOR

2001 ◽  
Vol 16 (supp01c) ◽  
pp. 1091-1093 ◽  
Author(s):  
TIMOTHY K. NELSON
Keyword(s):  
Impact Parameter ◽  
Support Structure ◽  
Physics Program ◽  
Silicon Sensors ◽  
Fine Pitch ◽  
Silicon System ◽  
The Impact ◽  
Radiation Tolerant

The CDF Layer 00 detector consists of single-sided silicon sensors assembled on the beampipe, forming the innermost of eight silicon layers in the CDF detector for Run II of the Fermilab Tevatron. Radiation tolerant p-in-n silicon with 25(50) μm implant(readout) pitch are mounted on a lightweight, cooled support structure and connect to electronics outside the tracking volume via long, fine-pitch cables. Layer 00 will significantly improve the impact parameter resolution and enhance the longevity of the silicon system, benefitting a large portion of the physics program for Run II.

scholarly journals STUDY OF A MA16-BASED VERTEX TRIGGER FOR THE CDF EXPERIMENT

1995 ◽  
Vol 06 (05) ◽  
pp. 681-692
Author(s):  
R. ODORICO
Keyword(s):  
Neural Network ◽  
Response Time ◽  
Impact Parameter ◽  
Electronic Components ◽  
The Neural Network ◽  
Viable Solution ◽  
Impact Parameters ◽  
Input Variables ◽  
Better Than

A Neural Network trigger for [Formula: see text] events based on the SVT microvertex processor of experiment CDF at Fermilab is presented. It exploits correlations among track impact parameters and azimuths calculated by the SVT from the SVX microvertex detector data. The neural trigger is meant for implementation on the systolic Siemens microprocessor MA16, which has already been used in a neural-network trigger for experiment WA92 at CERN. A suitable set of input variables is found, which allows a viable solution for the preprocessing task using standard electronic components. The response time of the neural-network stage of the trigger, including preprocessing, can be estimated ~10 μs. Its precise value depends on the quantitative specifications of the output signals of the SVT, which is still in development. The performance of the neural-network trigger is found to be significantly better than that of a conventional trigger exclusively based on impact parameter data.

Collisions between liquid drops

1978 ◽  
Vol 287 (1349) ◽  
pp. 635-675 ◽  
Keyword(s):  
Simple Model ◽  
Impact Parameter ◽  
Water Drop ◽  
Free Fall ◽  
Electrostatic Energy ◽  
Good Effect ◽  
Frequency Distributions ◽  
Input Parameters ◽  
The Impact ◽  
Drop Charge

An experiment is described in which pairs of water drops of different size were caused to collide during free fall at a velocity equal to the difference of their terminal velocities in still air. The collision parameters of trajectory, drop size, and drop charge were controlled with precision, and impacts of a particular kind could be reproduced indefinitely. By using synchronized flash photography, well in excess of 30000 measurements were taken from more than 10000 frames of film of the resulting behaviour of the water-drop pairs. Data are discussed in terms of an impact parameter, X which defines the relative trajectory of the drops in the centre-of-mass frame, and three energy parameters e C , e R and e T which delineate the properties electrostatic energy, rotational energy, and total energy of the two-drop system before impact. Input parameters were confined to values appropriate to natural rainfall. After collision four basic types of rotation occurred, the particular kind of rotation depending upon X , e C , e R and e T . Measured rates of rotation were compared with that to be expected from a simple model of inelastic collision between solid spheres and showed a marked resemblance. Distributions of mass after collision were compared with a model based upon a bimodal Gaussian distribution to good effect. In addition, frequency distributions of the number of drop products resulting from a given collision were prepared showing the controlling influence of the impact parameter, X , and the effect of varying drop charge. Relations were also established between statistical values for the coalescence efficiency of a given drop pair and the input parameters; however, while all results were consistent and reproducible, the effect of drop charge could not be demonstrated by a simple model.

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