The v(5) antisymmetric stretching vibration of (1) Sigma(g)(+) C-9 has been observed using direct infrared diode laser absorption spectroscopy of a pulsed supersonic cluster beam. Twenty-eight rovibrational transitions measured in the region of 2079-2081 cm(-1) were assigned to this band. A combined least squares fit of these transitions with previously reported v(6) transitions yielded the following molecular constants for the v(5) band : v(0)=2 079.673 58(17) cm(-1), B "=0.014 321 4(10) cm(-1), and B’=0.014 288 9(10) cm(-1). The IR intensity of the v(5) band relative to v(6) was found to be 0.108+/-0.006. Theoretical predictions for the relative intensities vary widely depending upon the level of theory employed, and the experimental value reported here is in reasonable agreement only with the result obtained from the most sophisticated ab initio calculation considered (CCSD).