An experimental comparison of rotational temperature and gas kinetic temperature in a H-2 discharge

An experimental comparison of rotational temperatures determined from optical emission spectroscopy (OES) of H-2 with the gas kinetic temperature is reported. A positive column H-2 discharge in a high-temperature oven is used. The oven temperature, determined with a thermocouple, provides a lower bound for the gas kinetic temperature. A thermal conduction calculation using the total power input to the discharge provides an upper bound for the gas kinetic temperature. A range of gas temperatures and pressures is explored. Two bands of molecular hydrogen were examined: the R branch of the G(1) Sigma(g)(+) --> B-1 Sigma(u)(+) (0, 0) band and the R branch of the d(3)II(u) --> a(3) Sigma(g)(+) (0, 0) Fulcher band. Measurements of the rotational temperature using emission from the G --> B band fall within the gas kinetic temperature bounds for temperatures above 800 degrees C. Data from the Fulcher band do not show a correlation with the gas temperature and give a constant rotational temperature independent of oven temperature.