With the enhanced sensitivity of Photothermal Deflection Spectroscopy (PDS),vibrational overtone spectra have been obtained in organic thin films forthe first time, covering the range from the near IR to the visible (0.4 - 2eV). The absorption spectra of polycarbonate, for instance, exhibits C-I1stretch modes for Δn> I where n is thevibrational quantum level. Previous measurements were constrained to eitherlong fibers, which pose the problem of various scattering losses not relatedto absorption, or to a restricted wavelength region in the visibleaccessible by dye laser sources. The unparalleled sensitivity of PDS allowsprecise determination of frequency, lineshape and intensity of the variousmodes, even for films ∼10μm thick over a broad energy range. The overtonespectra can be used as a probe of various basic molecular properties. In amanner similar to NMR spectroscopy, it is possible to study specific atomicbonds.