Stimulated emission depletion studies of molecular probe dynamics

R. J. Marsh; N. D. Leonczek; D. A. Armoogum; E. M. Monge; A. J. Bain

doi:10.1117/12.634088

12 September 2005 Stimulated emission depletion studies of molecular probe dynamics

R. J. Marsh, N. D. Leonczek, D. A. Armoogum, E. M. Monge, A. J. Bain

Proceedings Volume 5925, Nanophotonic Materials and Systems II; 59250C (2005) https://doi.org/10.1117/12.634088
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Stimulated emission depletion (STED) population and polarisation dynamics are used to determine <α₄₀> the degree of hexadecapole alignment created in ensembles of rhodamine 6G molecules in solution following two-photon excitation. Hexadecapole molecular alignment is an unavoidable consequence of two-photon excitation but is not observed in spontaneous emission. For a single element diagonal transition tensor measurements of the fluorescence anisotropy R(t) in systems undergoing small step isotropic rotational diffusion can in principle be used to determine <α₄₀>. STED measurements of rhodamine 6G yield a value for <α₄₀> that is larger than that predicted for a single element transition tensor (SXX). Recent work in our laboratory indicates that whilst SXX is dominant SYY, SXY and SYX are finite, measurements of <α₄₀> appear to be a sensitive probe of the structure of the two-photon transition tensor. STED and fluorescence anisotropy measurements are extended to Rhodamine 6G in the isotropic phase of 5CB a system where small step isotropic rotational relaxation does not take place. Here the values of <α₄₀> are considerably larger. These results are discussed in terms of the initial hexadecapole alignment and <α₄₀> relaxation dynamics in a restricted geometry.

Citation Download Citation

R. J. Marsh, N. D. Leonczek, D. A. Armoogum, E. M. Monge, and A. J. Bain "Stimulated emission depletion studies of molecular probe dynamics", Proc. SPIE 5925, Nanophotonic Materials and Systems II, 59250C (12 September 2005); https://doi.org/10.1117/12.634088

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