The propargyl radical (CH2C=CH) produced by the ArF excimer laser photolysis of allene was observed by time-resolved infrared diode laser spectroscopy. More than one hundred and fifty absorption lines have been assigned to the nu(6) (CH2-wagging) fundamental band of propargyl, Most of the absorption lines were observed as doublers due to the spin-rotation interaction in the B-2(1) ground electronic state. The rotational and spin-rotation interaction constants derived for the ground vibrational state are, A(0)=9.608 47(36), B-0=0.317 674(24), C-0=0.307 098(24), epsilon(aa)=-0.017 58(95), and epsilon(bb)=-0.000 355(76) cm(-1), when the figures in parentheses are 2.5 times standard deviations to be attached to the last digit. The nu(6) band origin is 687.176 03(62) cm(-1) consistent with the infrared spectrum observed in the argon matrix. Anomalously large vibrational changes in the A rotational constant and the Delta(K) centrifugal distortion constant are accounted for by the a-type Coriolis interaction between the nu(6) and nu(10) states, where nu(10) is the CH2-rocking vibration.