Abstract This paper reports the temporal change in the absorption of SF 6 when it interacts with short pulses of 10,6 μm radiation at 300°K. A novel pump-probe technique, using a train of pulses of the P(20) line, where each pulse acts as a probe for the previous pump pulse, was employed for the study. It was found, surprisingly, that the absorption increases when it is pumped by a single short pulse (5 ns FWHM and fluence varying from 0.02 mJ cm 2 to 0.4 mJ cm 2 ) but decreases when pumped by two such pulses. The extent of this change also depends on the time delay between the pulses. This experiment also gives an insight into the V-V relaxation rates of levels below 1000cm −1.