rotational relaxation time, \(\rho\)
Parameter describing the time-dependence of the tumbling of a molecular entity in a medium of viscosity η as originally defined by Debye, and used by Perrin in the original development of the theories of rotational motion of fluorophores.
Related to the rotational correlation time, \(\tau_{c}\), by \(\rho = 3\tau_{c}\). Thus, in the case of a spherically emitting species reorienting itself in a homogeneous fluid, \(\rho = 1/(6\, D_{r})\), with \(D_{r}\) the @R05411@.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 416 (