Abstract
By using the metastable time-of-flight technique (MTOF), experiments were carried out to determine the temperatures of extremely rarefied Ar and N2 gases at temperatures ranging from 300 to 550 K and at pressures of 10-5 Torr or lower. Temperatures were calculated from the time spectra obtained for Ar gas within the accuracy of ±3 K on the assumption that the Ar atoms excited onto the metastable states have a Maxwellian velocity distribution. Temperatures of N2 gas were obtained also within the accuracy of ±3 K; in this case some metastable states of N2 molecules are considered to have a mean life time of 160 µs due to radiative decays.