Title: Characteristics of a magneto-optical trap of molecules,
Abstract: We present the properties of a magneto-optical trap (MOT) of CaF molecules.
We study the process of loading the MOT from a decelerated buffer-gas-cooled
beam, and how best to slow this molecular beam in order to capture the most
molecules. We determine how the number of molecules, the photon scattering
rate, the oscillation frequency, damping constant, temperature, cloud size and
lifetime depend on the key parameters of the MOT, especially the intensity and
detuning of the main cooling laser. We compare our results to analytical and
numerical models, to the properties of standard atomic MOTs, and to MOTs of SrF
molecules. We load up to $2 \times 10^4$ molecules, and measure a maximum
scattering rate of $2.5 \times 10^6$ s$^{-1}$ per molecule, a maximum
oscillation frequency of 100 Hz, a maximum damping constant of 500 s$^{-1}$,
and a minimum MOT rms radius of 1.5 mm. A minimum temperature of 730 $\mu$K is
obtained by ramping down the laser intensity to low values. The lifetime,
typically about 100 ms, is consistent with a leak out of the cooling cycle with
a branching ratio of about $6 \times 10^{-6}$. The MOT has a capture velocity
of about 11 m/s.