  We use multiple quantum (MQ) NMR dynamics of a gas of spin-carrying molecules
in nanocavities at high and low temperatures for an investigation of
many-particle entanglement. A distribution of MQ NMR intensities is obtained at
high and low temperatures in a system of 201 spins 1/2. The second moment of
the distribution, which provides a lower bound on the quantum Fisher
information, sheds light on the many-particle entanglement in the system. The
dependence of the many-particle entanglement on the temperature is
investigated. Almost all spins are entangled at low temperatures.
