Rotational correlation time

Rotational correlation time (
 
 
 
 
 τ
 
 c
 
 
 
 
 {\displaystyle \tau _{c}}
 
) is the average time it takes for a <a href="/facts/Molecule/N9ljSfFq">molecule</a> to rotate one <a href="/facts/Radian/Srd38Sxa">radian</a>.
 In solution, rotational correlation times are in the order of <a href="/facts/Picosecond/62W8DK3Q">picoseconds</a>. For example, the 
 
 
 
 
 τ
 
 c
 
 
 =
 
 
 {\displaystyle \tau _{c}=}
 
 1.7 ps for water, and 100 ps for a pyrroline nitroxyl radical in a DMSO-water mixture. Rotational correlation times are employed in the measurement of <a href="/facts/Microviscosity/oQNMt6nw">microviscosity</a> (viscosity at the molecular level) and in protein characterization.
Rotational correlation times may be measured by <a href="/facts/Rotational_spectroscopy/QakXReKL">rotational (microwave)</a>, <a href="/facts/Dielectric_spectroscopy/BYQ9lQu0">dielectric</a>, and <a href="/facts/Nuclear_magnetic_resonance_spectroscopy/SFKgdthI">nuclear magnetic resonance</a> (NMR) spectroscopy. Rotational correlation times of probe molecules in media have been measured by <a href="/facts/Fluorescence/qsJVT2qP">fluorescence</a> lifetime or for <a href="/facts/Radical_(chemistry)/qFymuVoT">radicals</a>, from the linewidths of <a href="/facts/Electron_spin_resonance/TDHV8c9e">electron spin resonances</a>.

Rotational correlation time open-in-new

Rotational correlation time