Bifurcations of equilibrium points and periodic orbits are common in nonlinear dynamical systems when some parameters change. The vibrational motions of a molecule are nonlinear, and the bifurcation phenomena are seen in spectroscopy and chemical reactions. Bifurcations may lead to energy localization in specific bonds, and thus, they have important consequences for elementary chemical reaction...

Bleaching relaxation in lead salt (PbS) quantum dots (QDs) of various sizes and under different pump intensities has been studied. The observed bleaching relaxation features (particularly, shortening of the bleaching relaxation times with a decrease in the QD size and an increase of the pump-light intensity) are explained in the context of the proposed spectroscopic model. The model takes into ...

For a given excited state there exist densities that arise from more than one external potential. This is due to a qualitatively different energy-density relationship from that of the ground state and is related to positive eigenvalues in the nonlocal susceptibility for excited states. Resulting problems with the generalization of the density functional methodology to excited states are discussed.

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of 1,3,5-triazine at different wavelengths of the absorbed photon. Reaction pathways leading to various decomposition products have been mapped out at the G3(MP2,CC)//B3LYP level, and then the RRKM and microcanonical variational transition state theories have been applied ...

The static potential in the confinement “phase” of the SU(2) Higgs model is studied. In particular, the observation of the screening (called string breaking) of the static quarks by the dynamical light quarks leading to the formation of two static-light mesons was not observed before my work in non-Abelian gauge theories. The tool that I employ is lattice gauge simulation. The observable from w...

6.1 Harmonic Oscillator Reif §6.1: A simple harmonic one-dimensional oscillator has energy levels given by E n = (n + 1 2)ω, where ω is the characteristic (angular) frequency of the oscillator and where the quantum number n can assume the possible integral values n = 0, 1, 2,. . .. Suppose that such an oscillator is in thermal contact with a heat reservoir at temperature T low enough so that kT...

Nonlinear microscopy has become an important tool for imaging biological samples such as neurons. In two photon fluorescence, a fluorophore absorbs two photons at a low energy state, one of its electrons briefly converts to a higher energy state, and it emits a single excited photon at an energy level higher than that of the absorbed photons. In second harmonic generation (SHG), laser light is ...

We show that the crossover from the weak interaction limit towards the strong interaction limit may be accompanied by a delocalization eeect in one dimensional disordered quantum models. The spin degrees of freedom are frozen and the spatial wave functions remain symmetric or antisymmetric when the strength U of a short range interaction is varied. The study concerns the excited states for two ...

Electronic relaxation dynamics subsequent to s→p excitation of the excess electron in large anionic water clusters, H2O n − and D2O n − with 25 n 200, were investigated using time-resolved photoelectron imaging. Experimental improvements have enabled considerably larger clusters to be probed than in previous work, and the temporal resolution of the instrument has been improved. New trends are s...

Absorption bands in the visible region of the spectrum (350 700 nm) correspond to transitions from the ground state of a molecule to an excited electronic state which is 160 to 280 kJ above the ground state. In many substances, the lowest excited electronic state is more than 280 kJ above the ground state and no visible spectrum is observed. Those compounds which are colored (i.e., absorb in th...