Laser Spectroscopy and Molecular Collisions (Measurement of a Pressure-Broadening Coefficient)

The widths of IR absorption peaks of a gas are broadened when the pressure is increased, due to molecular collisions. The pressure-broadening coefficient (PBC) is a parameter that describes this broadening. Using a high-resolution, home-built, laser-based absorption spectrometer, we are focusing on the PBC of the 000-301(2) P30 absorption line of carbon dioxide at 6321.2046 wavenumbers, with nitrogen as the colliding gas. An etalon is used to produce fringes for triggering data collection at known wavenumber increments, and a Herriott cell is used to contain the gas, giving a spectroscopic path length of roughly 30 meters after reflections between the mirrors. Recent improvements have been made to our system, including a new soldered circuit board which may reduce electrical noise, and a new pressure gauge, allowing us to take data at higher pressures. Also, the implementation of a new gas mixing method has improved the consistency of our results at these higher pressures