An isolated TL glow peak, obtained using a linear heating rate, can be characterized by some parameters as can be seen in the figure below.

Fig. 9: The geometrical parameters characterizing an isolated peak.

As a first approach, it is possible to check the symmetry properties of the peak:

• a first-order peak has an asymmetrical shape.

• a second-order peak is characterized by a symmetrical shape.

According to the figure, the following parameters can be defined:

• T _M, T ₁, T ₂: are respectively the peak temperature at the maximum and the temperatures on either side of the temperature at the maximum, corresponding to half intensity,

• ?=T _M ?T ₁: is the half-width at the low temperature side of the peak,

• ?=T ₂ ?T _M : is the half-width towards the fall-off of the glow peak,

• ?=T ?T ₁: is the total half-width,

• : is the symmetrical geometrical factor.

It has to be noted that:

• According to the asymmetrical property of a first-order peak, ? is almost 50% bigger than ?,

• The geometrical factor _g is equal to 0.42 for a first-order kinetics, and 0.52 in the case of a second-order, hence, the following relation can be deduced

  (1)

  and two possibilities can be obtained. If relation (1) is less than zero, a second-order kinetics or a tendency has to be considered; if relation (1) results to be positive, a first-order...