  This paper is devoted to the construction and study of an equilibrium
Glauber-type dynamics of infinite continuous particle systems. This dynamics is
a special case of a spatial birth and death process. On the space $\Gamma$ of
all locally finite subsets (configurations) in ${\Bbb R}^d$, we fix a Gibbs
measure $\mu$ corresponding to a general pair potential $\phi$ and activity
$z>0$. We consider a Dirichlet form $ \cal E$ on $L^2(\Gamma,\mu)$ which
corresponds to the generator $H$ of the Glauber dynamics. We prove the
existence of a Markov process $\bf M$ on $\Gamma$ that is properly associated
with $\cal E$. In the case of a positive potential $\phi$ which satisfies
$\delta{:=}\int_{{\Bbb R}^d}(1-e^{-\phi(x)}) z dx<1$, we also prove that the
generator $H$ has a spectral gap $\ge1-\delta$. Furthermore, for any pure Gibbs
state $\mu$, we derive a Poincar\'e inequality. The results about the spectral
gap and the Poincar\'e inequality are a generalization and a refinement of a
recent result by L. Bertini, N. Cancrini, and F. Cesi.
