It represents the \b[squared <orbital angular momentum>]. In <atomic units>, $\hbar=1$, so its <eigenvalues> are $l(l+1)$. In ordinary units the corresponding observable is $\hbar^2l(l+1)$, with <orbital angular momentum quantum number> $l=0,1,2,\ldots$.

Solution

Past exam of the chemistry A course of the University of Cambridge / 2021 / Paper 1 / A1 / b / i / Solution

 Solution (source code)