Metallic nanoparticles are known to dramatically modify the spontaneous emission of nearby fluorescent molecules and materials. Here we examine the role of the nanoparticle plasmon resonance energy and nanoparticle scattering cross section on the fluorescence enhancement of adjacent indocyanine green (ICG) dye molecules. We find that enhancement of the molecular fluorescence by more than a factor of 50 can be achieved for ICG next to a nanoparticle with a large scattering cross section and a plasmon resonance frequency corresponding to the emission frequency of the molecule.

We show that an Au nanoshell with a pH-sensitive molecular adsorbate functions as a standalone, all-optical nanoscale pH meter that monitors its local environment through the pH-dependent surface-enhanced Raman scattering (SERS) spectra of the adsorbate molecules. Moreover, we also show how the performance of such a functional nanodevice can be assessed quantitatively. The complex spectral output is reduced to a simple device characteristic by application of a locally linear manifold approximation algorithm. The average accuracy of the nano-"meter" was found to be +/-0.10 pH units across its operating range.

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Exact quantum-mechanical calculations of the transition probabilities for the collinear collision of an atom with a diatomic molecule are performed. The diatomic molecule is treated as a harmonic oscillator. A range of interaction potentials from very hard to very soft are considered. It is found that for ``realistic'' interaction potentials the approximate calculations of Jackson and Mott are consistently high, even when the transition probabilities are low and good approximate results are expected. In some cases double and even triple quantum jumps are more important than single quantum jumps. Comparisons are made with exact classical calculations. A semiempirical formula is given for computing quantum-mechanical transition probabilities from classical calculations.

The renormalized Numerov method, which was recently developed and applied to the one-dimensional bound state problem [B. R. Johnson, J. Chem. Phys. 67, 4086 (1977)], has been generalized to compute bound states of the coupled-channel Schroedinger equation. Included in this presentation is a generalization of the concept of a wavefunction node and a method for detecting these nodes. By utilizing node count information it is possible to converge to any specific eigenvalue without the need of an initial close guess and also to calculate degenerate eigenvalues and determine their degree of degeneracy. A useful interpolation formula for calculating the eigenfunctions at nongrid points is also given. Results of example calculations are presented and discussed. One of the example problems is the single center expansion calculation of the 1sσg and 2sσg states of H+2.

A detailed investigation is made into the use of adiabatic approximations for describing excited stretching and bending vibrations of the water molecule. The goal is to determine precisely how effective this approach can be in a fully quantum mechanical triatomic calculation which incorporates anharmonicities to all orders in each of the modes. Great care is taken to avoid introducing unnecessary limitations or approximations: (i) Curvilinear coordinates are used rather than the Cartesian coordinates which form the starting point for normal mode calculations; (ii) the exact quantum kinetic energy operator in these coordinates is used as the basis for both the adiabatic and full three-dimensional calculations; (iii) a Sorbie–Murrell-type potential energy surface is used, giving a reasonable representation of the ground electronic surface for large excursions from the equilibrium configuration. In addition to the bond and bond-angle variables of earlier local mode investigations, a slightly different set of fully curvilinear coordinates is also investigated. These coordinates are shown to provide a more nearly separable description in both the exact and adiabatic treatments of this specific problem. The conventional adiabatic approach, in which the slower bending mode experiences an effective force due to averaging over the faster stretching modes, is reaffirmed to be accurate for excited stretching states. For states with any appreciable bending excitation, however, it turns out that the adiabatic calculations quickly erode in reliability. In answer to this problem, the reverse adiabatic procedure (with the bend treated first) is also implemented here. While counterintuitive, this latter method is found to yield a significant improvement for the calculated bending overtones, as well as many of the combination bands. Thus, by thorough consideration of both the coordinates and order of averaging employed, the adiabatic method is shown to be very effective for either bending or stretching overtones in a realistic, fully anharmonic, triatomic vibrational problem. In addition, introduction of a new orthonormal set of basis functions for the bending angle overcomes some of the problems associated with use of the less flexible Legendre basis.

Resonance Raman spectroscopy as a probe of the early stages in the dissociation dynamics of polyatomic molecules has become a valuable complement to photofragmentation studies. While these spontaneous Raman experiments are obtained in the frequency domain, they often reflect evolution of the molecule during the first few femtoseconds of bond breaking. Coupled with progress in classical and quantum calculations of large-amplitude motion, unique insights have become available for a number of small polyatomic molecules. The development of this field to date is reviewed.