Centrifugal effects in reaction rate theory

Binding energies for the inner hydration shells of Ca2+: An experimental and theoretical investigation of Ca2+(H2O)x complexes (x=5–9)

“…The data analysis program used (CRUNCH) accurately accounts for the charge on the ion in determining the location of the centrifugal barrier. The 2D external rotations are treated adiabatically, but include centrifugal effects [47]. Here, the adiabatic 2D external rotational energy of the EM is calculated using a statistical distribution with an explicit summation over the possible values of the rotational quantum number [37].…”

Microcanonical analysis of the kinetic method. The meaning of the “apparent entropy”

“…To examine the ⌬⌬S(T) ϭ ⌬⌬S ‡ (T) assumption in detail, consider a barrierless dissociation process characterized by a loose transition state where the vibrational frequencies and internal rotational constants of the transition states are identical to those of the products and where the transition state is located at the centrifugal barrier for dissociation [30]. Then ⌬⌬S vib (T) ϭ ⌬⌬S vib ‡ (T) is exactly true for the vibrational contributions to the entropy differences because the vibrational frequencies of the transitions states are the same as for the products.…”

“…However, the rotational constant for the overall rotation of the transition state complex at the centrifugal barrier depends on the angular momentum, which is conserved between the energized molecule and the transition state. The treatment of Waage and Rabinovitch [30] for this degree of freedom can be applied to the barrierless ion-induced-dipole potential, as also discussed by Rodgers et al [31]. Using eq 14 of reference [30] defining the partition function for the overall rotation of the pseudodiatomic transition state complex, Q cent ‡ (T), and the ioninduced-dipole potential, V(r) ϭ Ϫ␣q 2 /(4 0 ) 2 2r 4 , one obtains the entropy difference for the rotation in eq 8,…”

Some aspects of theory and experiment in the ethane–methyl radical system

“…Note that for Eo (recomb) = 0 kcal/mole, a simple collision theory treatment gives E A~~ = f R T = 0.3 kcal at 300°K, while a treatment that includes centrifugal effects leads to a prediction [41], [42] that A depends on so that EA,, = BRT = 0.1 kcal. It should be understood that while an E A~~ of 2 kcal at 300'K (Table 111) is compatible (for an appropriate activated complex model) in ART theory with EO (recomb) = 0 kcal/mole, such a model would no longer be compatible with a simple collision theory description.…”