| We constructed a novel spectroscopic system to study rotationally inelastic collisions involving truly thermal molecular ions at low temperatures. This system utilizes magnetic confinement to generate abundant concentrations of ions and time-resolved double resonance (pump-probe) techniques to study rotational energy transfer. With this system, we studied chemical and physical processes involving HCO+ and CO+ in gas mixtures containing H2 and CO. We measured the relaxation cross section for the J=2 state of HCO+ in collisions with normal-H2 at temperatures around 40 K and 77 K. The cross sections at the lower temperature are slightly below those predicted by Langevin theory, while those at the higher temperature are in good agreement with this theory. This dissertation discusses the discrepancy of the acquired data with Langevin theory at lower temperatures.;We also performed rotational energy level spectroscopic studies of the methyl formate and symmetric mono-deuterated methyl formate molecules. We developed a rho-axis method (RAM) analysis to accurately model the rotational-torsional spectrum for the ground torsional state. In this work, we report the first measurement and analysis of millimeter-wave (mmw) and submillimeter-wave (submmw) rotational-torsional transitions for mono-deuterated methyl formate. Additionally, we extended the spectral analysis of methyl formate to higher angular momentum and higher spectral frequencies than previously reported. |
