Student Summer Scholars

Diode-laser-based Measurement of a Fundamental Molecular Parameter: The Pressure Broadening Coefficient

Todd Major, Grand Valley State University
Stephanie Schaertel, Grand Valley State University


A fundamental understanding of chemical reactions requires a detailed knowledge of energy transfer during molecular collisions. Like measuring blood pressure in order to determine heart health, measuring the pressure broadening coefficient between two gases furthers the understanding of the energy transfer between two molecules. The goal of this research is to develop a diode-laser-based technique to measure the pressure broadening coefficient of CO2 in air. The measurement of the pressure broadening coefficient requires a non-linear least squares fit of a complicated function. In order to facilitate the fit, experimental techniques were developed to estimate parameters that can not be directly measured. Under normal circumstances, the pressure broadening coefficient of CO2 in air can be obtained successfully. We have measured a pressure broadening coefficient of CO2 in air of 0.094 +/- 0.003 cm-1/atm. The literature value is 0.0952 cm-1/atm, according to the HITRAN database. We are currently exploring the reproducibly of our measurement.