  A gap exists in microscopic understanding the dynamic properties of the
rotational organic cation (ROC) in the inorganic framework of the metal halide
perovskites (MHP) to date. Herein, we develop a microscopic theory of Raman
scattering for the ROC in MHP based on the angular momentum of a ROC exchanging
with that of the photon and phonon. We systematically present the selection
rules for the angular momentum transfer among three lowest rotational levels.
We find that the phonon angular momentum that arising from the inorganic
framework and its specific values could be directly manifested by Stokes (or
anti-Stokes) shift. Moreover, the initial orientation of the ROC and its
preferentially rotational directions could be judged in Raman spectra. This
study lays the theoretical foundation for the high-precision resolution and
manipulation of molecular rotation immersed in many-body environment by Raman
technique.
