Overtone spectroscopy in the gas phase by vibrationally assisted dissociation and photofragment ionization (OSVADPI) has been coupled with mass spectrometric detection of fragments enabling us to separate congested spectra into components arising from several naturally occurring isotopomers. The new technique of isotope selective overtone spectroscopy (ISOS) has been applied to the 4(1) component of the CCl3 chromophore absorption near 11385 cm(-1) in CHCl3 at room temperature and in supersonic jet expansions. These spectra allow us to assign a close local resonance with a CCl3 frame mode indicating vibrational energy redistribution within some ps. This is to be compared with the ultrafast (ca. 50 fs) redistribution between the CH stretching and bending modes established previously.