Stopping molecular rotation using coherent ultra-low-energy magnetic manipulations.

Rotational motion lies at the heart of intermolecular, molecule-surface chemistry and cold molecule science, motivating the development of methods to excite and de-excite rotations. Existing schemes involve perturbing the molecules with photons or electrons which supply or remove energy comparable to the rotational level spacing. Here, we study the possibility of de-exciting the molecular rotation of a D2 molecule, from a J=2 to the non-rotating J=0 state, without using an energy-matched perturbation. We show that a magnetic field which splits the rotational projection states by only pico eV, can change the probability that a molecule-surface collision will stop a molecule from rotating and lose rotational energy which is 9 orders larger than that of the magnetic manipulation. Calculations confirm the origin of the control scheme, but also underestimate rotational flips (Δm_J≠0), highlighting the importance of the results as a sensitive benchmark for further developing theoretical models of molecule-surface interactions.

Stochastic Adsorption of Diluted Solute Molecules at Interfaces

<div> <p>Here an analytical solution of Fick’s 2^nd law is used to predict the diffusion and the stochastic adsorption of single diluted solute molecules on flat and patterned surfaces. The equations are then compared to the results of several numerical Monte Carlo simulations using a random walk model. The 1D diffusion simulations clarify that the dependence of the solute-surface collision rate on the observation-time (measurement time resolution) is because of the multiple collisions of the same molecules over different time regions. It also surprisingly suggests that due to the self-mimetic fractal function of diffusion, the equation should be corrected by a factor of two. The absorption rate of solute on an adsorptive surface is found to follow a power-law decay function due to an evolving concentration gradient near the surface along with the depletion of the bulk solute molecules on the surface, for example, in a self-assembled monolayer adsorption kinetics. Thus, the analytical equations developed to calculate the collision at a fixed measuring frequency can be extended to map the whole curve over time. In the last section of this work, 3D diffusion simulations suggest that the analytical solution is valid to predict the adsorption rate of the bulk solute to a small group of adsorptive target molecules/area on a bouncing surface, which is a critical process in analyzing the kinetics of many bio-sensing platforms.</p> </div>

Application of the Concave Arc Surface Collision Detection Method to Virtual Assembly

Exact location calculation between each part of a parallel groove clamp when connecting a power line with a jumper is addressed in this paper. The relative location between a concave clamp and convex power line cannot be measured directly in live-line manipulation. We propose a concave arc surface collision detection method embedded in motion simulation. The relative location between irregular concave parts in the manipulation process can be obtained. The method is found to be computationally less expensive than convex partitioning collision detection techniques. This research provides a foundation for further study on robot hand manipulation with irregular assembly.

Collision of Bubbles with Solid Surface in the Presence of Specific Surfactants

The present work is motivated by the effort to understand basic processes occurring in three-phase systems where small bubbles interact with large particles. The simplified system of a single bubble rising in a stagnant liquid and colliding with a solid surface is studied. The effect of two specific surfactants, α-Terpineol and n-Octanol, is investigated. Two independent measurements are combined: (i) bubble–solid surface collision experiments and (ii) the bubble shape oscillations induced by a movable capillary. Both experiments are based on high-speed imaging resulting in the evaluation of the restitution coefficient characterizing the collision process and the relative damping time characterizing the bubble shape oscillations in the presence of surfactants. It was observed that even for small concentrations of a surfactant, both the bubble shape oscillations and the bubble bouncing on the solid surface are significantly suppressed. Two predictions for the restitution coefficient are proposed. The equations include a term characterizing the suppression of the damping time in the presence of surfactants and a term balancing the inertia, capillary and viscous forces in the liquid film separating the bubble and the solid surface. The proposed equations successfully predict the restitution coefficient of bubble bouncing on the solid surface in liquids with the addition of specific surfactants.

Stochastic Adsorption of Diluted Solute Molecules at Interfaces

<div> <p>Here an analytical solution of Fick’s 2^nd law is used to predict the diffusion and the stochastic adsorption of single diluted solute molecules on flat and patterned surfaces. The equations are then compared to the results of several numerical Monte Carlo simulations using a random walk model. The 1D diffusion simulations clarify that the dependence of the solute-surface collision rate on the observation-time (measurement time resolution) is because of the multiple collisions of the same molecules over different time regions. It also surprisingly suggests that due to the self-mimetic fractal function of diffusion, the equation should be corrected by a factor of two. The absorption rate of solute on an adsorptive surface is found to follow a power-law decay function due to an evolving concentration gradient near the surface along with the depletion of the bulk solute molecules on the surface, for example, in a self-assembled monolayer adsorption kinetics. Thus, the analytical equations developed to calculate the collision at a fixed measuring frequency can be extended to map the whole curve over time. In the last section of this work, 3D diffusion simulations suggest that the analytical solution is valid to predict the adsorption rate of the bulk solute to a small group of adsorptive target molecules/area on a bouncing surface, which is a critical process in analyzing the kinetics of many bio-sensing platforms.</p> </div>

Stochastic Adsorption of Diluted Solute Molecules at Interfaces

<div> <p>Here an analytical solution of Fick’s 2^nd law is used to predict the diffusion and the stochastic adsorption of single diluted solute molecules on flat and patterned surfaces. The equations are then compared to the results of several numerical Monte Carlo simulations using a random walk model. The 1D diffusion simulations clarify that the dependence of the solute-surface collision rate on the observation-time (measurement time resolution) is because of the multiple collisions of the same molecules over different time regions. It also surprisingly suggests that due to the self-mimetic fractal function of diffusion, the equation should be corrected by a factor of two. The absorption rate of solute on an adsorptive surface is found to follow a power-law decay function due to an evolving concentration gradient near the surface along with the depletion of the bulk solute molecules on the surface, for example, in a self-assembled monolayer adsorption kinetics. Thus, the analytical equations developed to calculate the collision at a fixed measuring frequency can be extended to map the whole curve over time. In the last section of this work, 3D diffusion simulations suggest that the analytical solution is valid to predict the adsorption rate of the bulk solute to a small group of adsorptive target molecules/area on a bouncing surface, which is a critical process in analyzing the kinetics of many bio-sensing platforms.</p> </div>