IR-IR double resonance experiments were used to study the state-to-state rotational relaxation of CO with CO, He, and Ne as collision partners. Individual rotational lines of the (2 - 0) vibrational overtone band were pumped by a pulsed IR laser and the subsequent rotational relaxation was monitored using a cw source. The resulting data sets were analyzed by fitting to numerical solutions of the master equation. State-to-state rate constant matrices were generated using fitting law functions. Fitting laws based on the modified exponential gap (MEG) and statistical power exponential gap (SPEG) and energy corrected sudden with exponential power (ECS-EP) models were used. Rate constant matrices for CO+He and CO+Ne were generated from scattering calculations that employed the appropriate <i>ab initio</i> potential energy surfaces. These theoretical rate constant matrices yielded kinetic simulations that agreed with the data nearly as well as the fitted MEG model and were unique in their ability to reproduce both the rotational energy transfer and pressure broadening data for CO+He and CO+Ne.
Single frequency laser sources, which also provide tunability, have wide use in spectroscopy and remote sensing as well as for other applications such as optical pumping. Optical parametric oscillators (OPOs) offer the potential for broadly tunable output in spectral regions inaccessible by conventional laser sources. We report here on the design and use ot an OPO architecture developed to produce pulsed, tunable, single-frequency output in the mid-infrared spectral region and used for optical pumping of gas. Design information about two separate OPOs that were developed will be presented along with experimental details of the optical pumping of CO on the (3-0) band around 1.57 μm and on the (2-0) band around 2.3 μm.