Photodissociation experiments are carried out for single HBr molecules which are 
embedded in the interior or absorbed on the surface of large Ar$_n$ clusters. 
For the embedded case the size dependence is measured for the average sizes 
n=51, 139, 230, 290, and 450. For the surface case and the average size 
n=139 the cluster temperature is varied by changing the source temperature from 
T=163 K to 263 K. The measured kinetic energy of the H atom fragments is measured 
exhibiting peaks at zero and 1.3 eV which mark completely caged and unperturbed 
fragments, respectively. The results are compared with Molecular Dynamics simulations 
which  account for the quantum librational delocalization of the HBr molecule. 
The location of the molecule in/on the cluster is obtained from a 
trajectory study of the pick-up
process under realistic conditions. For the embedded case corresponding to a 
co-expansion experiment, three argon layers are sufficient to completely hinder 
the H atom, in perfect agreement with the calculations. For the pick-up experiment, 
the best agreement is obtained for simulations assuming  equal contributions 
from HBr at the surface and in the subsurface argon layer.