This dissertation presents the findings of two experimental investigations in ultracold atomic and molecular physics: The study of the dual species trap loss in a rubidium - metastable argon magneto-optical trap and the photoassociative spectroscopy of ultracold metastable argon. The interspecies trap loss rate coefficients have been measured for ultracold collisions between 85 Rb and 40Ar* in a dual-species magneto-optical trap (MOT) and the two rates have been found to be approximately equal over the range of intensities studied with values of beta'Rb--Ar* = 3.0 +/- 1.3 x 10-11 cm 3/s and beta'Ar*--Rb = 1.9 +/- 0.9 x 10-11 cm3/s where beta' Rb--Ar* is the trap loss coefficient for Rb in the presence of Ar* and beta'Ar*--Rb is the reciprocal term. In addition, the trap loss rate coefficient for cold collisions in a metastable argon MOT alone have been measured with an average value of beta Ar* = 5.2 +/- 1.6 x 10-10 cm 3/s. Using a quadrupole mass spectrometer, the production of Ar +, A+2 , Rb+, and RbAr+ ions in the dual MOT have been observed, clearly identifying heteronuclear Penning and associative ionization as trap loss mechanisms. In the second experiment, the first ever investigation of the photoassociative (PA) spectroscopy of Ar* has been made. The exploratory study focuses on PA spectroscopy near the 4s[3/2]2 + 4p[5/2]3 asymptote of the Ar2* diatomic molecule over a 10 GHz range red detuned of the atomic resonance. With a range of probe laser intensities from ∼ 102--10 5ISat, 12 resonances have been observed. The spectra have been analyzed using the near-dissociation LeRoy-Bernstein method. Through this analysis, the spectra seem to best correlate with excitations to the 5g state.
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