Radial Velocities of Three Poorly Studied Clusters and the Kinematics of
  Open Clusters
  We present radial velocities for stars in the field of the open star clusters
Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained using the
Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope. These clusters are of
intermediate age (1-3 Gyr), located within the solar Galactocentric radius, and
have no previous radial velocity measurements. We find mean radial velocities
of -9.6 +/- 3.0 km s^-1, 48.1 +/- 2.0 km s^-1, and 12.4 +/- 2.8 km s^-1 for Be
44, Be 81, and NGC 6802, respectively. We present an analysis of radial
velocities of 134 open clusters of a wide range of ages using data obtained in
this study and the literature. Assuming the system of clusters rotates about
the Galactic center with a constant velocity, we find older clusters exhibit a
slower rotation and larger line-of-sight (LOS) velocity dispersion than younger
clusters. The gradual decrease in rotational velocity of the cluster system
with age is accompanied by a smooth increase in LOS velocity dispersion, which
we interpret as the effect of heating on the open cluster system over time.
