rate coefficients that are about two orders of magnitude larger than the experimental results for $T<200$ K. The less anisotropic BMKPE PES yields results in better agreement with the experimental results. The agreement is very good at $T=300$ K. At lower temperatures, the calculations predict slightly larger values than the experimental results. For $T > 300$ K, the experimental result is higher than the theoretical results on the BMKPE PES.

Rotational excitation and de-excitation in H$_2(v=0,j=0,2)$ + H$_2(v=0,j=0,2)$ collisions
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![ Elastic and inelastic cross sections as functions of the collision energy. Upper panel: Elastic cross sections for H$_2(v=0,j=0)$ + H$_2(v=0,j=0)$ collisions. Middle panel: Elastic and inelastic cross sections for H$_2(v=0,j=2)$ + H$_2(v=0,j=0)$ collisions. Lower panel: Elastic and inelastic cross sections for H$_2(v=0,j=2)$ + H$_2(v=0,j=2)$ collisions. \[XSEL-ULE-0000-0200-0202-FIG\]](XSEL_H2-H2-allJ-vj0000-1nKto120K.eps "fig:"){height="5.5cm"} ![ Elastic and inelastic cross sections as functions of the collision energy. Upper panel: Elastic cross sections for H$_2(v=0,j=0)$ + H$_2(v=0,j=0)$ collisions. Middle panel: Elastic and inelastic cross sections for H$_2(v=0,j=2)$ + H$_2(v=0,j=0)$ collisions. Lower panel: Elastic and inelastic cross sections for H$_2(v=0,j=2)$ + H$_2(v=0,j=2)$ collisions. \[XSEL-ULE-0000-0200-0202-FIG\]](XSELIN_H2-H2-allJ-vj0002-1nKto120K.eps "fig:"){height="5.5cm"} ![ Elastic and inelastic cross sections as functions of the collision energy. Upper panel: Elastic cross sections for H$_2(v=0,j=0)$ + H$_2(v=0,j=0)$ collisions. Middle panel: 