  The formation of angulon, stemming from the rotor (molecule or impurity)
rotating in the quantum many-body field, adds a new member in the
quasiparticle's family and has aroused intensively interests in multiple
research fields. However, the analysis of the coupling strength between the
rotor and its hosting environment remains a challenging task both in theory and
experiment. Here, we develop the all-coupling theory of the angulon by
introducing an unitary transformation, where the renormalization of the
rotational constants for different molecules in the helium nanodroplets are
reproduced, getting excellent agreement with the collected experimental data
during the past decades. Moreover, the strength of molecule-helium coupling and
the effective radius of the solvation shell corotating along with the molecular
rotor could be estimated qualitatively. This model not only provides the
significant enlightenment for analyzing the rotational spectroscopy of
molecules in the phononic environment, but also provides a new method to study
the transfer of the phonon angular momentum in angulon frame.

Mesoscale and Nanoscale Physics;Quantum Physics