Quantum mechanical investigation of N+N2 collision: state-to-state non-reaction and exchange reaction probabilities and rate constants

We present a state-to-state dynamical calculation on the exchange reaction N+N2→N2+N and the non-reaction N+N2→N+N2 based on the potential energy surface published by Mankodi et al. The calculation is performed using the time-independent quantum reaction scattering program. The reactivity of both reaction processes is discussed by reaction properties of vibrational quantum numbers v=0-3 and rotational quantum numbers j=0-32 (such as cumulative reaction probability, state-to-state reaction probabilities, and cross sections of N exchange, state-to-state rate constants for both reactions). The threshold energy of the exchange reaction can decrease with the decrease of vibrational excitation or the increase of rotational excitation. By using the J-shifting approximation, rate constants are reported for both reactions. The comparison of the presented total rate constant of the N+N2 exchange reaction with the previous results shows that the quantum effect is not negligible at low temperatures. For the exchange reaction, the rate constant at 500K decreases by about 10 orders of magnitude when the vibrational level of N2 increases from 0 to 7, indicating that the rate constants are sensitive to the initial vibrational level of N2 at low temperatures. For non-reactive collisions, the rate constants have little effect on the initial ro-vibrational levels of N2 at low temperatures.

Time-dependent quantum dynamics study of the F + C2H6 → HF + C2H5 reaction

The reaction probabilities, integral cross sections, energy efficiency and rate constants are investigated for the F + C2H6 reaction with a quantum reaction dynamics, wave-packet method. The ground-state integer cross...

Ultra-fast Dynamics in Quantum Systems Revealed by Particle Motion as Clock

To explore ultra-fast dynamics in quantum systems one needs detection schemes which allow time measurements in the attosecond regime. During the recent decades, the pump & probe two-pulse laser technique has provided milestone results on ultra-fast dynamics with femto- and attosecond time resolution. Today this technique is applied in many laboratories around the globe, since complete pump & probe systems are commercially available. It is, however, less known or even forgotten that ultra-fast dynamics has been investigated several decades earlier even with zeptosecond resolution in ion-atom collision processes. A few of such historic experiments, are presented here, where the particle motion (due to its very fast velocity) was used as chronometer to determine ultra-short time delays in quantum reaction processes. Finally, an outlook is given when in near future relativistic heavy ion beams are available which allow a novel kind of “pump & probe” experiments on molecular systems with a few zeptosecond resolution. However, such experiments are only feasible if the complete many-particle fragmentation process can be imaged with high momentum resolution by state-of-the-art multi-particle coincidence technique.

ON AN APPROACH TO THE DERIVATION OF CONSTITUTIVE EQUATIONS OF PHOTOCHROMIC MATERIALS

The paper presents constitutive equations of deformed solids, the state parameters of which, apart from the displacement vector, include concentrations of photochromic compounds. Equilibrium equations are completed with chemical kinetic equations, which are a system of, in a general case, nonlinear ordinary differential equations or parabolic-type equations accounting for the diffusion of products of photochromic reactions. Coefficients of such equations (for example, quantum reaction yield, reaction rate) can be assumed to depend on the stressed state. Several versions of the dependence of coefficients of chemical kinetic equations on the stressed-strained state are introduced. Also, in the assumption of electrostatics, possible effects of electric fields are taken into account. In analogy with mechanics of semiconductors and conductors, related equations of state are proposed. The introduced model of a coupled photo-electro-mechanical effect is a strongly nonlinear boundary-value problem, the equations of which contain a large number of material constants that must be determined experimentally. For conducting potential mechanical experiments, a simplified one-dimensional model is proposed, which is analogous to problems of tension-compression and bending in mechanics of bars and beams. In the framework thereof, solutions of related one-dimensional problems are constructed, which make it principally possible to define dimensionless complexes containing unknown material constants.

Multiphoton-gated cycloreversion reaction of a fluorescent diarylethene derivative as revealed by transient absorption spectroscopy

We report that the cycloreversion quantum reaction yield of a fluorescent diarylethene derivative is enhanced by a factor of >1800.