Trace rare gases optical emission spectroscopy has been used to measure the electron temperature, T-e, in a high-density inductively coupled Cl-2-Ar plasma at 18 mTorr as function of the 13.56 MHz radio frequency power and Ar fraction. Only the Kr and Xe emission lines were used to determine T-e, because of evidence of radiation trapping when the Ar emission lines were also used for larger At fractions. At 600 W (10.6 W cm(-2)), T-e increases from similar to4.0 +/- 0.5 eV to similar to6.0 +/-2.0 eV as the Ar fraction increases from 1% to 96%. In the H (inductive, bright) mode, T-e, for a "neat" chlorine plasma (including 1% of each He/Ne/Ar/Kr/Xe) increases only slightly from similar to3.8 to 4.0 eV as power increases from 450 to 750 W. This increase is much larger for larger Ar fractions, such as from similar to4.0 to 7.3 eV for 78% Ar. Most of these effects can be understood using the fundamental particle balance equation.