In this Letter, we report the near infrared spectrum of C-2 generated in AC hollow-cathode discharges of ethylene/helium mixtures using high resolution laser absorption spectroscopy with concentration modulation. The high sensitivity achieved by this zero-background technique allows the first detection of the very weak Delta v = -4 sequence of the d(3)Pi(g) -> a(3)Pi(u) system (Swan system). The detailed analysis of the spectrum between 13 750 and 14130 cm(-1) revealed that the (4,8) band was heavily perturbed. On the other hand, the (5,9) band was unperturbed to yield accurate molecular constants from least-squares fitting of the observed transitions. (C) 2012 Elsevier B.V. All rights reserved.