Emission anisotropy

{
  "id": "MLC-T-CHM-003849",
  "term": "Emission anisotropy",
  "field": "Chemistry",
  "definition": "A quantity describing the polarization of luminescence after excitation with linearly polarized light, defined as r = (I-par minus I-perp) divided by (I-par plus 2 I-perp), where the intensities are measured through a polarizer parallel and perpendicular to the excitation polarization. It reports how far the emitter rotates during its excited-state lifetime, so it rises with viscosity or when a probe binds a large molecule. For a randomly oriented sample the fundamental value runs from -0.2 to 0.4.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "additive",
    "angle",
    "anisotropy",
    "emission",
    "energy transfer",
    "fluorescence",
    "isotropic",
    "linear polarizer",
    "luminescence",
    "phosphorescence",
    "photoselection",
    "polarization",
    "radiant intensity",
    "rotational diffusion",
    "spectroscopy",
    "uniaxial sample"
  ],
  "references": [
    "PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 332 (https://doi.org/10.1351/pac200779030293)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/emission-anisotropy/"
}