Partridge-May Model (Zero-Order Kinetics)

Partridge and May have reported some observations concerning an apparent kinetic order less than the first one ( b<1).

If a single process is involved, one has the following equation

(1)

where c is the rate constant.

On the contrary, if b is less than 1, they explained such behavior by means of two competing processes: a first radiative order and a zero order without radiative transitions.

For such a model one can write:

(2)

where c ₂ is the zero-order rate constant.

The integration of Eq.(2) gets:

from which

(3)

where k' is a constant of integration.

The intensity is given by

(4)

Combining Eq.(3) and Eq.(4) one obtains

(5)

Partridge and May have reported that in isothermal decay experiments some data fitted Eq.(5) better than an equation expressing order higher than the first one.