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Time‐resolved two‐photon induced anisotropy decay: The rotational diffusion regime
Wan, Chaozhi Johnson, Carey K.
Wan, Chaozhi
Johnson, Carey K.
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Abstract
Two‐photon excitation (TPE) of randomly oriented chromophores in solution generates an anisotropic distribution. In a previous paper [Chem. Phys. 179, 513 (1994)], the polarization dependence of the TPE signal probed by a secondary spectroscopic transition (fluorescence or transient absorption) was determined. In this paper, the time dependence of anisotropic two‐photon induced fluorescence or transient absorption signals due to rotational diffusion is treated in spherical tensor formalism. The two‐photon signal in general contains isotropic (orientation independent) and anisotropic (orientation dependent) contributions. The latter decay with up to five exponential components. Four time‐dependent anisotropy parameters can be defined and measured, allowing additional information, not available in conventional one‐photon fluorescence depolarization measurements, to be determined. The special case of one‐color TPE is discussed in particular. It is shown that by measurement of the linear and circular anisotropiesr 1(t) and r 2(t), more than one rotational correlation time can be determined in many cases, providing information on rotational diffusion parameters not readily determined by analogous one‐photon methods and leading in some cases to resolution of rotational motion about the principal diffusion axes of the molecule.
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This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/101/12/10.1063/1.467908.
Date
1994-09-01
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American Institute of Physics
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Wan, Chaozhi; Johnson, Carey K. (1994). "Time‐resolved two‐photon induced anisotropy decay: The rotational diffusion regime." Journal of Chemical Physics, 101:10283-10291. http://dx.doi.org/10.1063/1.467908