We have measured the c(v? = 0 - 8)-X(v? = 0) laser excitation spectrum of the Hg-Ar van der Waals complex. This corresponds to the first observation of the bound Hg-rare-gas complex in the dark c state. In this measurement, we employ the sequence of two laser pulses; the complex is excited by the first one to the dark bound level in the c state and then successively excited by the second one to another bright state for the optical detection. The Birge-Sponer (BS) plot of the v? progression is well fitted by a straight line, suggesting that the c-state potential curve of Hg-Ar is well approximated by the Morse function. The linear fitting of this BS plot gives the potential parameters for the c state. ? 1998 American Institute of Physics.