This expression refers to the assumption, essential to conventional
transition-state theory,
that the energy of the system may be expressed as the sum of components associated
with different
degrees of freedom. In transition-state theory it is assumed that the energy of the motion of the system
through the
dividing surface of the
potential-energy surface is separable into various components. In many practical calculations it is assumed
that the energy of the system is separable into electronic, vibrational, rotational
and translational energy.
Source:
PAC, 1996, 68, 149
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC
Recommendations 1996))
on page 186