  We consider the possibility of constraining the lifetime of radiatively
decaying dark matter particles in clusters of galaxies inspired from generic
axions of the Kaluza-Klein type. Such axions have been invoked as a possible
explanation for the coronal X-ray emission from the Sun. These axions, or
similar particles, can be produced inside stars and some of them remain
confined by the deep gravitational potential of clusters of galaxies.
Specifically, we consider regions within merging galaxy clusters (Abell 520 and
the "Bullet Cluster"), where gravitational lensing observations have identified
massive, but baryon poor, structures. From an analysis of X-ray observations of
these mass concentrations, and the expected photon spectrum of decaying solar
KK-axions, we derive lower limits to the lifetime of such axions of tau approx.
10^23 sec. However, if KK-axions constitute less than a few percent of the dark
matter mass, this lifetime constraint is similar to that derived from solar
KK-axions.
