  We study the evaporation of stars from globular clusters using the simplified
Chandrasekhar model. This is an analytically tractable model giving reasonable
agreement with more sophisticated models that require complicated numerical
integrations. In the Chandrasekhar model: (i) the stellar system is assumed to
be infinite and homogeneous (ii) the evolution of the velocity distribution of
stars f(v,t) is governed by a Fokker-Planck equation, the so-called
Kramers-Chandrasekhar equation (iii) the velocities |v| that are above a
threshold value R>0 (escape velocity) are not counted in the statistical
distribution of the system. In fact, high velocity stars leave the system, due
to free evaporation or to the attraction of a neighboring galaxy (tidal
effects). Accordingly, the total mass and energy of the system decrease in
time. If the star dynamics is described by the Kramers-Chandrasekhar equation,
the mass decreases to zero exponentially rapidly. Our goal is to obtain
non-perturbative analytical results that complement the seminal studies of
Chandrasekhar, Michie and King valid for large times $t\to+\infty$ and large
escape velocities $R\to +\infty$. In particular, we obtain an exact
semi-explicit solution of the Kramers-Chandrasekhar equation with the absorbing
boundary condition f(R,t)=0. We use it to obtain an explicit expression of the
mass loss at any time t when $R\to +\infty$. We also derive an exact integral
equation giving the exponential evaporation rate $\lambda(R)$, and the
corresponding eigenfunction $f_{\lambda}(v)$, when $t\to +\infty$ for any
sufficiently large value of the escape velocity R. For $R\to +\infty$, we
obtain an explicit expression of the evaporation rate that refines the
Chandrasekhar results.
