  The diffusion of a bulk absorbed gas species out of spherical pebbles is
studied analytically, stressing the usefulness of the time integral of the
diffusion coefficient for analysis of arbitrary temperature schedule
experiments. Highly accurate approximations are introduced where the numeric
evaluation of the analytic expressions takes considerable time. A method is
proposed to extract the diffusion kinetic parameters from a single linear
heating ramp, namely, the activation energy of the diffusion coefficient and
the ratio of the corresponding preexponential factor to the radius of spherical
pebbles.
