The successful development of hypersonic vehicles requires detailed knowledge of the flow physics around the vehicle. Specifically, an understanding of the thermochemical nonequilibrium behavior is crucial for this flight regime. Additionally, the hypersonic flight regime involves an extremely high level of energy so a small error in the modeling of the energy processes can result in drastic changes in the vehicle design, which motivates modeling the physics involved at a high-fidelity. However, there is limited experimental data to assess the current nonequilibrium modeling approaches. Recently, the Hanson Group at Stanford University measured the formation of electronically excited atomic oxygen behind reflected shock waves using cavity-enhanced absorption spectroscopy. The motivation of this work is to develop a modeling approach that can be assessed using these experiments. In the present work, 1D post normal shock flow calculations of both pure and diluted molecular oxygen in argon are carried out and used to analyze existing shock tube experiments. State-of-the-art thermochemical nonequilibrium models, including two-temperature (2T) and multitemperature-collisional-radiative (MTCR) models are adopted in these post normal shock flow analyses. The 2T approach models the excited states using Boltzmann statistics at the vibrational temperature. The MTCR uses a four temperature approach (translational, rotational, vibrational, and electronic). The non-Boltzmann behavior of the excited states is modeled by including the relevant collisional and radiative mechanisms and then solving for the excited state concentrations using an electronic master equation coupling model.