[Measurement of rotational temperature in N2 DC glow discharge by optical emission spectroscopy]

Measurements of rotational temperature as low as several hundred Kelvin have been achieved using optical emission spectroscopy (OES) in nitrogen DC glow discharge. The strongest band of the first negative system of nitrogen molecule ion was chosen to determine the rotational temperature of nitrogen DC glow discharge at 4 different positions in the discharge area: back of the cathode; cathode sheath; positive column and anode glow region. In positive column the rotational temperature of N2+ increases apparently with the increasing discharge voltage from 500-1,100 V when the pressure is 10 Pa. However at pressure of 20 Pa the rotational temperature in positive column increases slightly with the increase of discharge voltage. On the contrary, the rotational temperature in cathode sheath takes reverse tendency when the discharge voltage varies from 500-1,100 V. As regard the anode glow region, the rotational temperature at 10 Pa decreases with the increase of discharge voltage, but that at the 20 Pa increases. We attribute the different changing tendencies of the rotational temperature to the different discharge status at different pressure. When the discharge voltage varies from 500 to 1,100 V, the discharge at pressure of 10 Pa is normal glow and that at 20 Pa is abnormal glow.