Nonstatistical Reaction Dynamics

2020 ◽  
Vol 71 (1) ◽  
pp. 289-313 ◽  
Author(s):  
Bhumika Jayee ◽  
William L. Hase
Keyword(s):  
Reaction Dynamics ◽  
Energy Partitioning ◽  
Degree Of Freedom ◽  
Atomic Motion ◽  
Vibrational States ◽  
Bimolecular Reactions ◽  
Regular Motion ◽  
Good Quantum Number ◽  
Reactant Molecule ◽  
Short Time

Nonstatistical dynamics is important for many chemical reactions. The Rice-Ramsperger-Kassel-Marcus (RRKM) theory of unimolecular kinetics assumes a reactant molecule maintains a statistical microcanonical ensemble of vibrational states during its dissociation so that its unimolecular dynamics are time independent. Such dynamics results when the reactant's atomic motion is chaotic or irregular. Intrinsic non-RRKM dynamics occurs when part of the reactant's phase space consists of quasiperiodic/regular motion and a bottleneck exists, so that the unimolecular rate constant is time dependent. Nonrandom excitation of a molecule may result in short-time apparent non-RRKM dynamics. For rotational activation, the 2J + 1 K levels for a particular J may be highly mixed, making K an active degree of freedom, or K may be a good quantum number and an adiabatic degree of freedom. Nonstatistical dynamics is often important for bimolecular reactions and their intermediates and for product-energy partitioning of bimolecular and unimolecular reactions. Post–transition state dynamics is often highly complex and nonstatistical.

scholarly journals Direct observation of bimolecular reactions of ultracold KRb molecules

Science ◽  
2019 ◽  
Vol 366 (6469) ◽  
pp. 1111-1115 ◽  
Author(s):  
M.-G. Hu ◽  
Y. Liu ◽  
D. D. Grimes ◽  
Y.-W. Lin ◽  
A. H. Gheorghe ◽  
...  
Keyword(s):  
Quantum State ◽  
Chemical Reactions ◽  
Reaction Dynamics ◽  
Velocity Map Imaging ◽  
Bimolecular Reactions ◽  
Quantum State Resolved ◽  
Trapped Gas ◽  
Short Time ◽  
Transient Intermediates ◽  
Mutual Collision

Femtochemistry techniques have been instrumental in accessing the short time scales necessary to probe transient intermediates in chemical reactions. In this study, we took the contrasting approach of prolonging the lifetime of an intermediate by preparing reactant molecules in their lowest rovibronic quantum state at ultralow temperatures, thereby markedly reducing the number of exit channels accessible upon their mutual collision. Using ionization spectroscopy and velocity-map imaging of a trapped gas of potassium-rubidium (KRb) molecules at a temperature of 500 nanokelvin, we directly observed reactants, intermediates, and products of the reaction 40K87Rb + 40K87Rb → K2Rb2* → K2 + Rb2. Beyond observation of a long-lived, energy-rich intermediate complex, this technique opens the door to further studies of quantum-state–resolved reaction dynamics in the ultracold regime.

H + CD4Abstraction Reaction Dynamics:  Product Energy Partitioning†

2006 ◽  
Vol 110 (9) ◽  
pp. 3017-3027 ◽  
Author(s):  
Wenfang Hu ◽  
György Lendvay ◽  
Diego Troya ◽  
George C. Schatz ◽  
Jon P. Camden ◽  
...  
Keyword(s):  
Reaction Dynamics ◽  
Energy Partitioning

scholarly journals Optical computing with soliton trains in Bose–Einstein condensates

2015 ◽  
Vol 26 (07) ◽  
pp. 1550082 ◽  
Author(s):  
Florian Pinsker
Keyword(s):  
Density Profile ◽  
Optical Computing ◽  
Degree Of Freedom ◽  
Atom Cloud ◽  
Additional Degree ◽  
Bose Einstein ◽  
Short Time ◽  
Phase Engineering

Optical computing devices can be implemented based on controlled generation of soliton trains in single and multicomponent Bose–Einstein condensates (BEC). Our concepts utilize the phenomenon that the frequency of soliton trains in BEC can be governed by changing interactions within the atom cloud [F. Pinsker, N. G. Berloff and V. M. Pérez-García, Phys. Rev. A87, 053624 (2013), arXiv:1305.4097]. We use this property to store numbers in terms of those frequencies for a short time until observation. The properties of soliton trains can be changed in an intended way by other components of BEC occupying comparable states or via phase engineering. We elucidate, in which sense, such an additional degree of freedom can be regarded as a tool for controlled manipulation of data. Finally, the outcome of any manipulation made is read out by observing the signature within the density profile.

Identification of Nonlinearities Using Computational Approaches

2016 ◽  
Vol 846 ◽  
pp. 559-564
Author(s):  
Joshua Critchley-Marrows ◽  
Samanvay Karambhe ◽  
Denzil Khan ◽  
Elias Vasilikas ◽  
Gareth A. Vio
Keyword(s):  
Computational Methods ◽  
Coulomb Friction ◽  
Degree Of Freedom ◽  
Nonlinear Behaviour ◽  
Computational Results ◽  
Computational Approaches ◽  
Short Time ◽  
Two Degree Of Freedom

This paper presents an analysis into the computational results for modelling of a two degree-of-freedom nonlinear vibrating structure. Fast Fourier Transformations, Short Time Fourier Transformations, Hilbert Transformations and wavelets are used to model this system. These techniques aim to locate and quantify the nonlinear behaviour of the system. Coulomb friction was detected with a number of these techniques, however other nonlinearities could not be detected. From the analysis conducted, improved computational methods are necessary for the detection of nonlinearities.

Energy partitioning and reaction dynamics in the chemiluminescent channel of the reaction: HS + O3 → HSO* + O2

1984 ◽  
Vol 110 (2) ◽  
pp. 183-190 ◽  
Author(s):  
D.J.W. Kendall ◽  
J.J.A. O'Brien ◽  
J.J. Sloan ◽  
R.Glen Macdonald
Keyword(s):  
Reaction Dynamics ◽  
Energy Partitioning

State- and bond-selected photodissociation and bimolecular reaction of water

1990 ◽  
Vol 332 (1625) ◽  
pp. 259-272 ◽  
Keyword(s):  
Room Temperature ◽  
Reaction Dynamics ◽  
Bimolecular Reaction ◽  
Water Molecules ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Stretching Vibration ◽  
Different Populations ◽  
H 20 ◽  
Selection Of

It is possible to exploit the isolation of the 0 —H stretching vibration in H 20 and HOD to control the photodissociation and reaction dynamics in water molecules excited in the region of the third overtone (4rOH) of the 0 -H stretch. In vibrationally mediated photodissociation of H 20, the selection of different initial stretching states having roughly the same energy leads to drastically different populations of the vibrational states of the OH photolysis product. By exciting the O-H stretching overtone in HOD, we can selectively photolyze that bond. In bimolecular reaction experiments, we react H 20 (4rOH) with H atoms to produce H 2 and OH. The reaction, which is endothermic, proceeds at an undetectable rate in our room temperature measurements. Vibrationally excited water, however, reacts at roughly the gas kinetic collision rate. Applying this technique to HOD (4rOH) allows us to demonstrate bond selected bimolecular chemistry in which the reaction produces only OD. This observation suggests a general approach to assessing bond controlled reactions in a variety of systems.

The kinetics of the thermal decomposition and polymerization of ethane and ethylene

1956 ◽  
Vol 233 (1195) ◽  
pp. 465-479 ◽  
Keyword(s):  
Nitric Oxide ◽  
Bimolecular Reaction ◽  
The Other ◽  
Constant Concentration ◽  
Time Intervals ◽  
Bimolecular Reactions ◽  
Higher Hydrocarbons ◽  
Products Of Reaction ◽  
Short Time ◽  
Kinetics Of

The pyrolysis of ethane, ethylene and mixtures of the two gases, has been studied by heating the reactants to 600° C for short time intervals and measuring the products of reaction by chemical analysis. In the case of ethane, the first products are ethylene, hydrogen and a small amount of methane. This reaction is inhibited by nitric oxide. The subsequent reactions, none of which is affected by nitric oxide, involve both ethane and ethylene, and result in the formation of methane (in far greater quantity than that produced from ethane direct), propylene, a compound of the formula C 4 H 8 which may be 1-butene, and higher hydrocarbons. The C 4 H 8 , which attains a constant concentration after a few minutes, is produced by two bimolecular reactions, one involving both ethane and ethylene, and the other ethylene alone. Methane is formed from decomposition of the C 4 H 8 . Propylene and higher hydrocarbons are produced as a result of a bimolecular reaction between C 4 H 8 and ethylene. The kinetics of the proposed mechanism hold good over the widest possible range of ethane + ethylene mixtures. Values for the velocity constants of all these reactions are given, and approximate values of the activation energies have been calculated following a further set of experiments at 450° C.

Sign in / Sign up

Export Citation Format

Share Document