OVERTONE SPECTRUM OF THE CH CHROMOPHORE IN CHI3

The infrared spectrum of iodoform vapor was measured between 900 and 1 0 000 cm(-1) in a heatable multipass cell with an interferometric Four ier transform spectrometer and temperatures up to 433 K. Twenty-five b ands (including hot bands) could be assigned as fundamentals, overtone , or combination bands of the CH stretching and bending vibrations. Th e observed data are interpreted in terms of variational calculations u sing internal and normal coordinates and some evidence is given for th e existence of a strong coupling constant \k(sbb)'\ = 50 cm(-1) betwee n the two vibrational modes with subpicosecond redistribution of energ y. Off-diagonal anharmonic constants between the CH stretching and ben ding manifold and the molecular frame vibrations have been determined. (C) 1995 American Institute of Physics.