Vibrational relaxation of aqueous CS2 formed by geminate recombination of CS+S after photolysis of CS2(aq) at 200 nm is studied by subpicosecond transient absorption spectroscopy. Comparison of the transient absorption measured from 200 to 313 nm with calculated absorption transients pertaining to vibrationally relaxing CS2 shows that relaxation to the vibrational ground state of CS2 predominantly occurs in the asymmetric stretch on a 5 ps time scale. (C) 2001 American Institute of Physics.