Close-coupling study of rotational energy transfer in H$_2$O collisions with He atoms

Due to the astrophysical importance of water and helium, the H$_2$O-He collisional system has been the subject of numerous experimental and theoretical studies. For numerical astrophysical models, quantitative determinations of state-to-state cross sections and rate coefficients for H$_2$O-He collisions are crucial. In this work quantum close-coupling scattering calculations of rotational energy transfer (RET) of rotationally excited H$_2$O due to collisions with He are presented for collision energies between 10$^{-6}$ and 1000 cm$^{-1}$ with para-H$_2$O initially in levels 1$_{1,1}$, 2$_{0,2}$, 2$_{1,1}$, 2$_{2,0}$, and ortho-H$_2$O in levels 1$_{1,0}$, 2$_{1,2}$, 2$_{2,1}$. Differential cross section, quenching cross sections and rate coefficients for state-to-state RET were computed on three new H$_2$O-He potential energy surfaces (PESs). The inelastic and elastic differential cross sections are also compared with available experimental measurements.