symbol: $\lt\!r_{\rm{o,f}}^2\!\gt$; units: $\pu{nm2}$, $\pu{m2}$
https://doi.org/10.1351/goldbook.12201
Mean-square end-to-end distance of a linear freely rotating chain.
Note: \(\lt\!r_{\rm{o,f}}^2\!\gt\) of a hypothetical, sufficiently long, linear freely rotating chain of identical single skeletal bonds is given by the equation \[\lt\!r_{\rm{o,f}}^{2}\!\gt = nl^{2}\frac{(1 + \cos \theta)}{(1 - \cos \theta)}\] where \(n\) is the number of skeletal bonds of length \(l\) and valence-angle supplement \(\theta\).