[Show abstract][Hide abstract] ABSTRACT: Fluorescence properties of submonolayers of rhodamine 6G have been measured as a function of distance to an aluminum mirror. For distances less than 5 nm (spacer layers of 1 nm thickness were used) a broadening of the emission spectrum is observed. The fluorescence lifetime has been measured for distances up to 6 nm. The broadening of the fluorescence spectra and the shortening of the lifetime observed when the sample is close to the mirror are attributed to efficient energy transfer from the monolayer to the mirror. The experiments clearly demonstrate that both volume and surface contributions must be considered in this energy-transfer process.
The Journal of Chemical Physics 04/1993; · 3.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Detailed measurements of the macroscopic second-order optical nonlinearity χ(2)(2ω,ω,ω) of Langmuir-Blodgett dye-doped monolayers are reported. The observed deviations from a linear behavior of χ(2) with increasing surface density are shown to be due to local-field effects. In order to calculate these local-field factors for disordered systems, a novel Monte Carlo type calculation is introduced. This calculation not only accounts for density variations in the monolayers but also incorporates the effect of off-diagonal elements of the (microscopic) linear susceptibility tensor. Quantitative agreement is found between the calculations and the experimental results using only the molecular hyperpolarizability as a free parameter. A method is presented to determine the tilt angle of the chromophores in Langmuir-Blodgett monolayers from the anisotropy of the linear absorption. The tilt angle determined this way is in excellent agreement with a determination by second-harmonic generation.
The Journal of Chemical Physics 01/1992; · 3.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present fluorescence spectra showing that the spontaneous-emission spectrum of a molecule in front of a mirror is not invariant on propagation. We also calculate the cross-spectral density of this light source and show that it does not obey Wolf’s scaling law.
[Show abstract][Hide abstract] ABSTRACT: We show that the spontaneous emission spectrum of a thin sample in front of a mirror exhibits Wiener-type fringes that contain information on the dephasing dynamics of the excited molecules. In order to probe these dynamics, the molecules must be excited with a short optical pulse or with a light field that has a correlation time shorter than the dephasing time constant T2. The technique is used to study the ultrafast dephasing of nile blue in a polymer matrix at room temperature. A homogeneous dephasing time constant T2 of 100±10 fs is obtained.
Chemical Physics Letters 06/1990; 169(5). · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We show that the fluorescence emitted in front of a mirror exhibits angular and spectral localization effects that are caused by self-interference in the spontaneous emission from a Wiener-fringe pattern. A semi-classical description is given and found to be in good agreement with the observations.