  Experimental search for molecular-nuclear transitions
H_2O\to^{18}Ne^*(4.522,1^-)\to^{18}F\to^{18}O in water molecules was carried
out. The measurements were performed in a low-background laboratory at the
Baksan Neutrino Observatory. Under the assumption that the above transitions
take place, the estimate for the half-life time of water molecule was found to
be about 10^{18} years.
