Tensor properties of the anharmonic oscillator model. Starting from Eq. (1.4.52), relevant to a collection of isotropic, centrosymmetric, anharmonic oscillators, show that the nonlinear susceptibility possesses the
![](https://test.transtutors.com/qimg/85c7e789-d51e-4479-9c34-8633fac8ca2b.png)
with all other elements vanishing. Give a simple physical argument that explains why the vanishing elements do vanish. Also, give a simple physical argument that explains why χijhl possesses off-diagonal tensor components, even though the medium is isotropic.
![](https://test.transtutors.com/qimg/8451d4ed-b14c-4e8a-9799-dc1d007efcea.png)