Chemical Control and Spectral Fingerprints of Electronic Coupling in Carbon Nanostructures

The optical and electronic properties of atomically thin materials such as single-walled carbon nanotubes and graphene are sensitively influenced by substrates, the degree of aggregation, and the chemical environment. However, it has been experimentally challenging to determine the origin and quantify these effects. Here we use time-dependent density-functional-theory calculations to simulate these properties for well-defined molecular systems. We investigate a series of core–shell structures containing C₆₀ enclosed in progressively larger carbon shells and their perhydrogenated or perfluorinated derivatives. Our calculations reveal strong electronic coupling effects that depend sensitively on the interparticle distance and on the surface chemistry. In many of these systems we predict considerable orbital mixing and charge transfer between the C₆₀ core and the enclosing shell. We predict that chemical functionalization of the shell can modulate the electronic coupling to the point where the core and shell are completely decoupled into two electronically independent chemical systems. Additionally, we predict that the C₆₀ core will oscillate within the confining shell, at a frequency directly related to the strength of the electronic coupling. This low-frequency motion should be experimentally detectable in the IR region

Inelastic Scattering of NO by Kr: Rotational Polarization over a Rainbow

We use molecular beams and ion imaging to determine quantum state resolved angular distributions of NO radicals after inelastic collision with Kr. We also determine both the sense and the plane of rotation (the rotational orientation and alignment, respectively) of the scattered NO. By full selection and then detection of the quantum parity of the NO molecule, our experiment is uniquely sensitive to quantum interference. For forward-scattered NO, we report hitherto unseen changes in the plane and sense of rotation with scattering angle and show, remarkably, that the rotation of the NO molecule after collision can be near-maximally oriented for certain transitions and scattering angles. These effects are enhanced by the full parity selection in the experiment and result from the interplay between attractive and repulsive forces