Automorphisms of Liouville Structures

By a Liouville structure on a symplectic manifold $(M, \omega)$ we mean a choice of symplectic potential: that is, a choice of one-form $\theta$ on $M$ such that ${\rm d} \theta = \omega$. We determine precisely all the automorphisms of a Liouville structure in case $(M, \omega)$ is a symplectic vector space and $\theta$ differs from its canonical symplectic potential by the differential of a homogeneous monomial.